Junit5User Guide

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JUnit 5 User Guide
Stefan Bechtold, Sam Brannen, Johannes Link, Matthias Merdes, Marc Philipp,
Christian Stein
Version 5.3.2

Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
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1.1. What is JUnit 5? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
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1.2. Supported Java Versions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
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1.3. Getting Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
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2. Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
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2.1. Dependency Metadata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
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2.2. Dependency Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
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2.3. JUnit Jupiter Sample Projects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
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3. Writing Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
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3.1. Annotations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
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3.2. Test Classes and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
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3.3. Display Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
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3.4. Assertions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
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3.5. Assumptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
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3.6. Disabling Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
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3.7. Conditional Test Execution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
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3.8. Tagging and Filtering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
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3.9. Test Instance Lifecycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
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3.10. Nested Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
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3.11. Dependency Injection for Constructors and Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
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3.12. Test Interfaces and Default Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
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3.13. Repeated Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
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3.14. Parameterized Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
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3.15. Test Templates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
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3.16. Dynamic Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
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3.17. Parallel Execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
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4. Running Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
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4.1. IDE Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
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4.2. Build Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
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4.3. Console Launcher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
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4.4. Using JUnit 4 to run the JUnit Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
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4.5. Configuration Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
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4.6. Tag Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
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4.7. Capturing Standard Output/Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
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5. Extension Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
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5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
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5.2. Registering Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
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5.3. Conditional Test Execution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
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5.4. Test Instance Factories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
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5.5. Test Instance Post-processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
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5.6. Parameter Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
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5.7. Test Lifecycle Callbacks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
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5.8. Exception Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
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5.9. Providing Invocation Contexts for Test Templates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
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5.10. Keeping State in Extensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
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5.11. Supported Utilities in Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
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5.12. Relative Execution Order of User Code and Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
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6. Migrating from JUnit 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
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6.1. Running JUnit 4 Tests on the JUnit Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
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6.2. Migration Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
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6.3. Limited JUnit 4 Rule Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
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7. Advanced Topics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
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7.1. JUnit Platform Launcher API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
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8. API Evolution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
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8.1. API Version and Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
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8.2. Experimental APIs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
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8.3. Deprecated APIs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
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8.4. @API Tooling Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
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9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
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10. Release Notes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Ê

1. Overview
The goal of this document is to provide comprehensive reference documentation for programmers
writing tests, extension authors, and engine authors as well as build tool and IDE vendors.

!

Translations

This document is also available in Simplified Chinese and Japanese.

1.1. What is JUnit 5?
Unlike previous versions of JUnit, JUnit 5 is composed of several different modules from three
different sub-projects.
JUnit 5 = JUnit Platform + JUnit Jupiter + JUnit Vintage
The JUnit Platform serves as a foundation for launching testing frameworks on the JVM. It also
defines the TestEngine API for developing a testing framework that runs on the platform.
Furthermore, the platform provides a Console Launcher to launch the platform from the command
line and build plugins for Gradle and Maven as well as a JUnit 4 based Runner for running any
TestEngine on the platform.
JUnit Jupiter is the combination of the new programming model and extension model for writing
tests and extensions in JUnit 5. The Jupiter sub-project provides a TestEngine for running Jupiter
based tests on the platform.
JUnit Vintage provides a TestEngine for running JUnit 3 and JUnit 4 based tests on the platform.

1.2. Supported Java Versions
JUnit 5 requires Java 8 (or higher) at runtime. However, you can still test code that has been
compiled with previous versions of the JDK.

1.3. Getting Help
Ask JUnit 5 related questions on Stack Overflow or chat with us on Gitter.

2. Installation
Artifacts for final releases and milestones are deployed to Maven Central.
Snapshot artifacts are deployed to SonatypeÕs snapshots repository under /org/junit.

2.1. Dependency Metadata

1

2.1.1. JUnit Platform
¥ Group ID: org.junit.platform
¥ Version: 1.3.2
¥ Artifact IDs:
junit-platform-commons
Internal common library/utilities of JUnit. These utilities are intended solely for usage within
the JUnit framework itself. Any usage by external parties is not supported. Use at your own
risk!
junit-platform-console
Support for discovering and executing tests on the JUnit Platform from the console. See
Console Launcher for details.
junit-platform-console-standalone
An executable JAR with all dependencies included is provided at Maven Central under the
junit-platform-console-standalone directory. See Console Launcher for details.
junit-platform-engine
Public API for test engines. See Plugging in your own Test Engine for details.
junit-platform-launcher
Public API for configuring and launching test plans!Ñ!typically used by IDEs and build tools.
See JUnit Platform Launcher API for details.
junit-platform-runner
Runner for executing tests and test suites on the JUnit Platform in a JUnit 4 environment. See
Using JUnit 4 to run the JUnit Platform for details.
junit-platform-suite-api
Annotations for configuring test suites on the JUnit Platform. Supported by the JUnitPlatform
runner and possibly by third-party TestEngine implementations.
junit-platform-surefire-provider
Support for discovering and executing tests on the JUnit Platform using Maven Surefire.

2.1.2. JUnit Jupiter
¥ Group ID: org.junit.jupiter
¥ Version: 5.3.2
¥ Artifact IDs:
junit-jupiter-api
JUnit Jupiter API for writing tests and extensions.
junit-jupiter-engine
JUnit Jupiter test engine implementation, only required at runtime.

2

junit-jupiter-params
Support for parameterized tests in JUnit Jupiter.
junit-jupiter-migrationsupport
Migration support from JUnit 4 to JUnit Jupiter, only required for running selected JUnit 4
rules.

2.1.3. JUnit Vintage
¥ Group ID: org.junit.vintage
¥ Version: 5.3.2
¥ Artifact ID:
junit-vintage-engine
JUnit Vintage test engine implementation that allows to run vintage JUnit tests, i.e. tests
written in the JUnit 3 or JUnit 4 style, on the new JUnit Platform.

2.1.4. Bill of Materials (BOM)
The Bill of Materials POM provided under the following Maven coordinates can be used to ease
dependency management when referencing multiple of the above artifacts using Maven or Gradle.
¥ Group ID: org.junit
¥ Artifact ID: junit-bom
¥ Version: 5.3.2

2.1.5. Dependencies
All of the above artifacts have a dependency in their published Maven POMs on the following @API
Guardian JAR.
¥ Group ID: org.apiguardian
¥ Artifact ID: apiguardian-api
¥ Version: 1.0.0
In addition, most of the above artifacts have a direct or transitive dependency to the following
OpenTest4J JAR.
¥ Group ID: org.opentest4j
¥ Artifact ID: opentest4j
¥ Version: 1.1.1

2.2. Dependency Diagram

3

org.junit.platform
junit-platform-runner

org.junit.jupiter
junit-jupiter-params

org.apiguardian
junit-platform-surefire-provider

junit-platform-console

org.junit.vintage
junit-jupiter-migrationsupport

junit-jupiter-engine

junit-vintage-engine

junit-jupiter-api

junit:junit

junit-platform-launcher

junit-platform-engine

apiguardian-api

All artifacts except
opentest4j and junit:junit
have a dependency on this
artifact. The edges have
been omitted from this
diagram for the sake of
readability.

junit-platform-suite-api

org.opentest4j
opentest4j

junit-platform-commons

2.3. JUnit Jupiter Sample Projects
The junit5-samples repository hosts a collection of sample projects based on JUnit Jupiter and JUnit
Vintage. YouÕll find the respective build scripts (e.g., build.gradle, pom.xml, etc.) in the projects
below.
¥ For Gradle and Java, check out the junit5-jupiter-starter-gradle project.
¥ For Gradle and Kotlin, check out the junit5-jupiter-starter-gradle-kotlin project.
¥ For Gradle and Groovy, check out the junit5-jupiter-starter-gradle-groovy project.
¥ For Maven, check out the junit5-jupiter-starter-maven project.
¥ For Ant, check out the junit5-jupiter-starter-ant project.

3. Writing Tests
A first test case

import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.jupiter.api.Test;
class FirstJUnit5Tests {
Ê
Ê
Ê
Ê

@Test
void myFirstTest() {
assertEquals(2, 1 + 1);
}

}

3.1. Annotations
JUnit Jupiter supports the following annotations for configuring tests and extending the framework.
All core annotations are located in the org.junit.jupiter.api package in the junit-jupiter-api
module.

4

Annotation

Description

@Test

Denotes that a method is a test method. Unlike JUnit 4Õs @Test annotation, this
annotation does not declare any attributes, since test extensions in JUnit
Jupiter operate based on their own dedicated annotations. Such methods are
inherited unless they are overridden.

@ParameterizedTest Denotes that a method is a parameterized test. Such methods are inherited
unless they are overridden.
@RepeatedTest

Denotes that a method is a test template for a repeated test. Such methods are
inherited unless they are overridden.

@TestFactory

Denotes that a method is a test factory for dynamic tests. Such methods are
inherited unless they are overridden.

@TestInstance

Used to configure the test instance lifecycle for the annotated test class. Such
annotations are inherited.

@TestTemplate

Denotes that a method is a template for test cases designed to be invoked
multiple times depending on the number of invocation contexts returned by
the registered providers. Such methods are inherited unless they are
overridden.

@DisplayName

Declares a custom display name for the test class or test method. Such
annotations are not inherited.

@BeforeEach

Denotes that the annotated method should be executed before each @Test,
@RepeatedTest, @ParameterizedTest, or @TestFactory method in the current class;
analogous to JUnit 4Õs @Before. Such methods are inherited unless they are
overridden.

@AfterEach

Denotes that the annotated method should be executed after each @Test,
@RepeatedTest, @ParameterizedTest, or @TestFactory method in the current class;
analogous to JUnit 4Õs @After. Such methods are inherited unless they are
overridden.

@BeforeAll

Denotes that the annotated method should be executed before all @Test,
@RepeatedTest, @ParameterizedTest, and @TestFactory methods in the current
class; analogous to JUnit 4Õs @BeforeClass. Such methods are inherited (unless
they are hidden or overridden) and must be static (unless the "per-class" test
instance lifecycle is used).

@AfterAll

Denotes that the annotated method should be executed after all @Test,
@RepeatedTest, @ParameterizedTest, and @TestFactory methods in the current
class; analogous to JUnit 4Õs @AfterClass. Such methods are inherited (unless
they are hidden or overridden) and must be static (unless the "per-class" test
instance lifecycle is used).

@Nested

Denotes that the annotated class is a nested, non-static test class. @BeforeAll
and @AfterAll methods cannot be used directly in a @Nested test class unless
the "per-class" test instance lifecycle is used. Such annotations are not
inherited.

@Tag

Used to declare tags for filtering tests, either at the class or method level;
analogous to test groups in TestNG or Categories in JUnit 4. Such annotations
are inherited at the class level but not at the method level.

@Disabled

Used to disable a test class or test method; analogous to JUnit 4Õs @Ignore. Such
annotations are not inherited.

5

Annotation

Description

@ExtendWith

Used to register custom extensions. Such annotations are inherited.

Methods annotated with @Test, @TestTemplate, @RepeatedTest, @BeforeAll, @AfterAll, @BeforeEach, or
@AfterEach annotations must not return a value.

"

Some annotations may currently be experimental. Consult the table in
Experimental APIs for details.

3.1.1. Meta-Annotations and Composed Annotations
JUnit Jupiter annotations can be used as meta-annotations. That means that you can define your
own composed annotation that will automatically inherit the semantics of its meta-annotations.
For example, instead of copying and pasting @Tag("fast") throughout your code base (see Tagging
and Filtering), you can create a custom composed annotation named @Fast as follows. @Fast can then
be used as a drop-in replacement for @Tag("fast").

import
import
import
import

java.lang.annotation.ElementType;
java.lang.annotation.Retention;
java.lang.annotation.RetentionPolicy;
java.lang.annotation.Target;

import org.junit.jupiter.api.Tag;
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Tag("fast")
public @interface Fast {
}

3.2. Test Classes and Methods
A test method is any instance method that is directly or meta-annotated with @Test, @RepeatedTest,
@ParameterizedTest, @TestFactory, or @TestTemplate. A test class is any top level or static member
class that contains at least one test method.

6

A standard test class

import static org.junit.jupiter.api.Assertions.fail;
import
import
import
import
import
import

org.junit.jupiter.api.AfterAll;
org.junit.jupiter.api.AfterEach;
org.junit.jupiter.api.BeforeAll;
org.junit.jupiter.api.BeforeEach;
org.junit.jupiter.api.Disabled;
org.junit.jupiter.api.Test;

class StandardTests {
Ê
Ê
Ê

@BeforeAll
static void initAll() {
}

Ê
Ê
Ê

@BeforeEach
void init() {
}

Ê
Ê
Ê

@Test
void succeedingTest() {
}

Ê
Ê
Ê
Ê

@Test
void failingTest() {
fail("a failing test");
}

Ê
Ê
Ê
Ê
Ê

@Test
@Disabled("for demonstration purposes")
void skippedTest() {
// not executed
}

Ê
Ê
Ê

@AfterEach
void tearDown() {
}

Ê
Ê
Ê

@AfterAll
static void tearDownAll() {
}

}

#

Neither test classes nor test methods need to be public.

7

3.3. Display Names
Test classes and test methods can declare custom display names!Ñ!with spaces, special characters,
and even emojis!Ñ!that will be displayed by test runners and test reporting.

import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
@DisplayName("A special test case")
class DisplayNameDemo {
Ê
Ê
Ê
Ê

@Test
@DisplayName("Custom test name containing spaces")
void testWithDisplayNameContainingSpaces() {
}

Ê
Ê
Ê
Ê

@Test
@DisplayName("!¡!¡"!")
void testWithDisplayNameContainingSpecialCharacters() {
}

Ê
Ê
Ê
Ê

@Test
@DisplayName(""")
void testWithDisplayNameContainingEmoji() {
}

}

3.4. Assertions
JUnit Jupiter comes with many of the assertion methods that JUnit 4 has and adds a few that lend
themselves well to being used with Java 8 lambdas. All JUnit Jupiter assertions are static methods
in the org.junit.jupiter.api.Assertions class.

import
import
import
import
import
import
import
import
import

static
static
static
static
static
static
static
static
static

java.time.Duration.ofMillis;
java.time.Duration.ofMinutes;
org.junit.jupiter.api.Assertions.assertAll;
org.junit.jupiter.api.Assertions.assertEquals;
org.junit.jupiter.api.Assertions.assertNotNull;
org.junit.jupiter.api.Assertions.assertThrows;
org.junit.jupiter.api.Assertions.assertTimeout;
org.junit.jupiter.api.Assertions.assertTimeoutPreemptively;
org.junit.jupiter.api.Assertions.assertTrue;

import org.junit.jupiter.api.Test;
class AssertionsDemo {

8

Ê
@Test
Ê
void standardAssertions() {
Ê
assertEquals(2, 2);
Ê
assertEquals(4, 4, "The optional assertion message is now the last parameter.
");
Ê
assertTrue('a' < 'b', () -> "Assertion messages can be lazily evaluated -- "
Ê
+ "to avoid constructing complex messages unnecessarily.");
Ê
}
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
void groupedAssertions() {
// In a grouped assertion all assertions are executed, and any
// failures will be reported together.
assertAll("person",
() -> assertEquals("John", person.getFirstName()),
() -> assertEquals("Doe", person.getLastName())
);
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
void dependentAssertions() {
// Within a code block, if an assertion fails the
// subsequent code in the same block will be skipped.
assertAll("properties",
() -> {
String firstName = person.getFirstName();
assertNotNull(firstName);

Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê

// Executed only if the previous assertion is valid.
assertAll("first name",
() -> assertTrue(firstName.startsWith("J")),
() -> assertTrue(firstName.endsWith("n"))
);
},
() -> {
// Grouped assertion, so processed independently
// of results of first name assertions.
String lastName = person.getLastName();
assertNotNull(lastName);

Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê

// Executed only if the previous assertion is valid.
assertAll("last name",
() -> assertTrue(lastName.startsWith("D")),
() -> assertTrue(lastName.endsWith("e"))
);

}

Ê
Ê

@Test
void exceptionTesting() {

}
);

9

Ê
Ê
Ê
Ê
Ê

}

Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
void timeoutNotExceeded() {
// The following assertion succeeds.
assertTimeout(ofMinutes(2), () -> {
// Perform task that takes less than 2 minutes.
});
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
void timeoutNotExceededWithResult() {
// The following assertion succeeds, and returns the supplied object.
String actualResult = assertTimeout(ofMinutes(2), () -> {
return "a result";
});
assertEquals("a result", actualResult);
}

Ê
Ê
Ê
Ê
Ê
Ê

@Test
void timeoutNotExceededWithMethod() {
// The following assertion invokes a method reference and returns an object.
String actualGreeting = assertTimeout(ofMinutes(2), AssertionsDemo::greeting);
assertEquals("Hello, World!", actualGreeting);
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
void timeoutExceeded() {
// The following assertion fails with an error message similar to:
// execution exceeded timeout of 10 ms by 91 ms
assertTimeout(ofMillis(10), () -> {
// Simulate task that takes more than 10 ms.
Thread.sleep(100);
});
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
void timeoutExceededWithPreemptiveTermination() {
// The following assertion fails with an error message similar to:
// execution timed out after 10 ms
assertTimeoutPreemptively(ofMillis(10), () -> {
// Simulate task that takes more than 10 ms.
Thread.sleep(100);
});
}

Ê

private static String greeting() {

10

Throwable exception = assertThrows(IllegalArgumentException.class, () -> {
throw new IllegalArgumentException("a message");
});
assertEquals("a message", exception.getMessage());

Ê
Ê

return "Hello, World!";
}

}
JUnit Jupiter also comes with a few assertion methods that lend themselves well to being used in
Kotlin. All JUnit Jupiter Kotlin assertions are top-level functions in the org.junit.jupiter.api
package.

11

import
import
import
import
import

org.junit.jupiter.api.Test
org.junit.jupiter.api.assertAll
org.junit.jupiter.api.Assertions.assertEquals
org.junit.jupiter.api.Assertions.assertTrue
org.junit.jupiter.api.assertThrows

class AssertionsKotlinDemo {
Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
fun `grouped assertions`() {
assertAll("person",
{ assertEquals("John", person.firstName) },
{ assertEquals("Doe", person.lastName) }
)
}

Ê
@Test
Ê
fun `exception testing`() {
Ê
val exception = assertThrows ("Should throw an
exception") {
Ê
throw IllegalArgumentException("a message")
Ê
}
Ê
assertEquals("a message", exception.message)
Ê
}
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
fun `assertions from a stream`() {
assertAll(
"people with name starting with J",
people
.stream()
.map {
// This mapping returns Stream<() -> Unit>
{ assertTrue(it.firstName.startsWith("J")) }
}
)
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê
}

@Test
fun `assertions from a collection`() {
assertAll(
"people with last name of Doe",
people.map { { assertEquals("Doe", it.lastName) } }
)
}

12

3.4.1. Third-party Assertion Libraries
Even though the assertion facilities provided by JUnit Jupiter are sufficient for many testing
scenarios, there are times when more power and additional functionality such as matchers are
desired or required. In such cases, the JUnit team recommends the use of third-party assertion
libraries such as AssertJ, Hamcrest, Truth, etc. Developers are therefore free to use the assertion
library of their choice.
For example, the combination of matchers and a fluent API can be used to make assertions more
descriptive and readable. However, JUnit JupiterÕs org.junit.jupiter.api.Assertions class does not
provide an assertThat() method like the one found in JUnit 4Õs org.junit.Assert class which accepts
a Hamcrest Matcher. Instead, developers are encouraged to use the built-in support for matchers
provided by third-party assertion libraries.
The following example demonstrates how to use the assertThat() support from Hamcrest in a JUnit
Jupiter test. As long as the Hamcrest library has been added to the classpath, you can statically
import methods such as assertThat(), is(), and equalTo() and then use them in tests like in the
assertWithHamcrestMatcher() method below.

import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.MatcherAssert.assertThat;
import org.junit.jupiter.api.Test;
class HamcrestAssertionDemo {
Ê
Ê
Ê
Ê

@Test
void assertWithHamcrestMatcher() {
assertThat(2 + 1, is(equalTo(3)));
}

}
Naturally, legacy tests based on the JUnit 4 programming model can continue using
org.junit.Assert#assertThat.

3.5. Assumptions
JUnit Jupiter comes with a subset of the assumption methods that JUnit 4 provides and adds a few
that lend themselves well to being used with Java 8 lambdas. All JUnit Jupiter assumptions are static
methods in the org.junit.jupiter.api.Assumptions class.

13

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assumptions.assumeTrue;
import static org.junit.jupiter.api.Assumptions.assumingThat;
import org.junit.jupiter.api.Test;
class AssumptionsDemo {
Ê
Ê
Ê
Ê
Ê

@Test
void testOnlyOnCiServer() {
assumeTrue("CI".equals(System.getenv("ENV")));
// remainder of test
}

Ê
Ê
Ê
Ê
Ê
Ê

@Test
void testOnlyOnDeveloperWorkstation() {
assumeTrue("DEV".equals(System.getenv("ENV")),
() -> "Aborting test: not on developer workstation");
// remainder of test
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
void testInAllEnvironments() {
assumingThat("CI".equals(System.getenv("ENV")),
() -> {
// perform these assertions only on the CI server
assertEquals(2, 2);
});

Ê
Ê
Ê

// perform these assertions in all environments
assertEquals("a string", "a string");
}

}

3.6. Disabling Tests
Entire test classes or individual test methods may be disabled via the @Disabled annotation, via one
of the annotations discussed in Conditional Test Execution, or via a custom ExecutionCondition.
HereÕs a @Disabled test class.

14

import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.Test;
@Disabled
class DisabledClassDemo {
Ê
@Test
Ê
void testWillBeSkipped() {
Ê
}
}
And hereÕs a test class that contains a @Disabled test method.

import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.Test;
class DisabledTestsDemo {
Ê
Ê
Ê
Ê

@Disabled
@Test
void testWillBeSkipped() {
}

Ê
Ê
Ê
}

@Test
void testWillBeExecuted() {
}

3.7. Conditional Test Execution
The ExecutionCondition extension API in JUnit Jupiter allows developers to either enable or disable a
container or test based on certain conditions programmatically. The simplest example of such a
condition is the built-in DisabledCondition which supports the @Disabled annotation (see Disabling
Tests). In addition to @Disabled, JUnit Jupiter also supports several other annotation-based
conditions in the org.junit.jupiter.api.condition package that allow developers to enable or
disable containers and tests declaratively. See the following sections for details.
Composed Annotations

Note that any of the conditional annotations listed in the following sections may

!

also be used as a meta-annotation in order to create a custom composed
annotation. For example, the @TestOnMac annotation in the @EnabledOnOs demo
shows how you can combine @Test and @EnabledOnOs in a single, reusable
annotation.

15

Each of the conditional annotations listed in the following sections can only be
declared once on a given test interface, test class, or test method. If a conditional

"

annotation is directly present, indirectly present, or meta-present multiple times
on a given element, only the first such annotation discovered by JUnit will be used;
any additional declarations will be silently ignored. Note, however, that each
conditional annotation may be used in conjunction with other conditional
annotations in the org.junit.jupiter.api.condition package.

3.7.1. Operating System Conditions
A container or test may be enabled or disabled on a particular operating system via the
@EnabledOnOs and @DisabledOnOs annotations.

@Test
@EnabledOnOs(MAC)
void onlyOnMacOs() {
Ê
// ...
}
@TestOnMac
void testOnMac() {
Ê
// ...
}
@Test
@EnabledOnOs({ LINUX, MAC })
void onLinuxOrMac() {
Ê
// ...
}
@Test
@DisabledOnOs(WINDOWS)
void notOnWindows() {
Ê
// ...
}
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Test
@EnabledOnOs(MAC)
@interface TestOnMac {
}

3.7.2. Java Runtime Environment Conditions
A container or test may be enabled or disabled on a particular version of the Java Runtime
Environment (JRE) via the @EnabledOnJre and @DisabledOnJre annotations.

16

@Test
@EnabledOnJre(JAVA_8)
void onlyOnJava8() {
Ê
// ...
}
@Test
@EnabledOnJre({ JAVA_9, JAVA_10 })
void onJava9Or10() {
Ê
// ...
}
@Test
@DisabledOnJre(JAVA_9)
void notOnJava9() {
Ê
// ...
}

3.7.3. System Property Conditions
A container or test may be enabled or disabled based on the value of the named JVM system property
via the @EnabledIfSystemProperty and @DisabledIfSystemProperty annotations. The value supplied
via the matches attribute will be interpreted as a regular expression.

@Test
@EnabledIfSystemProperty(named = "os.arch", matches = ".*64.*")
void onlyOn64BitArchitectures() {
Ê
// ...
}
@Test
@DisabledIfSystemProperty(named = "ci-server", matches = "true")
void notOnCiServer() {
Ê
// ...
}

3.7.4. Environment Variable Conditions
A container or test may be enabled or disabled based on the value of the named environment
variable from the underlying operating system via the @EnabledIfEnvironmentVariable and
@DisabledIfEnvironmentVariable annotations. The value supplied via the matches attribute will be
interpreted as a regular expression.

17

@Test
@EnabledIfEnvironmentVariable(named = "ENV", matches = "staging-server")
void onlyOnStagingServer() {
Ê
// ...
}
@Test
@DisabledIfEnvironmentVariable(named = "ENV", matches = ".*development.*")
void notOnDeveloperWorkstation() {
Ê
// ...
}

3.7.5. Script-based Conditions
JUnit Jupiter provides the ability to either enable or disable a container or test depending on the
evaluation of a script configured via the @EnabledIf or @DisabledIf annotation. Scripts can be
written in JavaScript, Groovy, or any other scripting language for which there is support for the
Java Scripting API, defined by JSR 223.

"

Conditional test execution via @EnabledIf and @DisabledIf is currently an
experimental feature. Consult the table in Experimental APIs for details.
If the logic of your script depends only on the current operating system, the

!

current Java Runtime Environment version, a particular JVM system property, or a
particular environment variable, you should consider using one of the built-in
annotations dedicated to that purpose. See the previous sections of this chapter for
further details.

#

18

If you find yourself using the same script-based condition many times, consider
writing a dedicated ExecutionCondition extension in order to implement the
condition in a faster, type-safe, and more maintainable manner.

@Test // Static JavaScript expression.
@EnabledIf("2 * 3 == 6")
void willBeExecuted() {
Ê
// ...
}
@RepeatedTest(10) // Dynamic JavaScript expression.
@DisabledIf("Math.random() < 0.314159")
void mightNotBeExecuted() {
Ê
// ...
}
@Test // Regular expression testing bound system property.
@DisabledIf("/32/.test(systemProperty.get('os.arch'))")
void disabledOn32BitArchitectures() {
Ê
assertFalse(System.getProperty("os.arch").contains("32"));
}
@Test
@EnabledIf("'CI' == systemEnvironment.get('ENV')")
void onlyOnCiServer() {
Ê
assertTrue("CI".equals(System.getenv("ENV")));
}
@Test // Multi-line script, custom engine name and custom reason.
@EnabledIf(value = {
Ê
"load('nashorn:mozilla_compat.js')",
Ê
"importPackage(java.time)",
Ê
"",
Ê
"var today = LocalDate.now()",
Ê
"var tomorrow = today.plusDays(1)",
Ê
"tomorrow.isAfter(today)"
Ê
},
Ê
engine = "nashorn",
Ê
reason = "Self-fulfilling: {result}")
void theDayAfterTomorrow() {
Ê
LocalDate today = LocalDate.now();
Ê
LocalDate tomorrow = today.plusDays(1);
Ê
assertTrue(tomorrow.isAfter(today));
}

Script Bindings
The following names are bound to each script context and therefore usable within the script. An
accessor provides access to a map-like structure via a simple String get(String name) method.
Name

Type

Description

systemEnvironment

accessor

Operating system environment variable accessor.

19

Name

Type

Description

systemProperty

accessor

JVM system property accessor.

junitConfiguration accessor
Parameter

Configuration parameter accessor.

junitDisplayName

String

Display name of the test or container.

junitTags

Set

All tags assigned to the test or container.

junitUniqueId

String

Unique ID of the test or container.

3.8. Tagging and Filtering
Test classes and methods can be tagged via the @Tag annotation. Those tags can later be used to
filter test discovery and execution.

3.8.1. Syntax Rules for Tags
¥ A tag must not be null or blank.
¥ A trimmed tag must not contain whitespace.
¥ A trimmed tag must not contain ISO control characters.
¥ A trimmed tag must not contain any of the following reserved characters.
" ,: comma
" (: left parenthesis
" ): right parenthesis
" &: ampersand
" |: vertical bar
" !: exclamation point

#

In the above context, "trimmed" means that leading and trailing whitespace
characters have been removed.

import org.junit.jupiter.api.Tag;
import org.junit.jupiter.api.Test;
@Tag("fast")
@Tag("model")
class TaggingDemo {
Ê
Ê
Ê
Ê
}

20

@Test
@Tag("taxes")
void testingTaxCalculation() {
}

3.9. Test Instance Lifecycle
In order to allow individual test methods to be executed in isolation and to avoid unexpected side
effects due to mutable test instance state, JUnit creates a new instance of each test class before
executing each test method (see Test Classes and Methods). This "per-method" test instance lifecycle
is the default behavior in JUnit Jupiter and is analogous to all previous versions of JUnit.

#

Please note that the test class will still be instantiated if a given test method is
disabled via a condition (e.g., @Disabled, @DisabledOnOs, etc.) even when the "permethod" test instance lifecycle mode is active.

If you would prefer that JUnit Jupiter execute all test methods on the same test instance, simply
annotate your test class with @TestInstance(Lifecycle.PER_CLASS). When using this mode, a new test
instance will be created once per test class. Thus, if your test methods rely on state stored in
instance variables, you may need to reset that state in @BeforeEach or @AfterEach methods.
The "per-class" mode has some additional benefits over the default "per-method" mode. Specifically,
with the "per-class" mode it becomes possible to declare @BeforeAll and @AfterAll on non-static
methods as well as on interface default methods. The "per-class" mode therefore also makes it
possible to use @BeforeAll and @AfterAll methods in @Nested test classes.
If you are authoring tests using the Kotlin programming language, you may also find it easier to
implement @BeforeAll and @AfterAll methods by switching to the "per-class" test instance lifecycle
mode.

3.9.1. Changing the Default Test Instance Lifecycle
If a test class or test interface is not annotated with @TestInstance, JUnit Jupiter will use a default
lifecycle mode. The standard default mode is PER_METHOD; however, it is possible to change the
default for the execution of an entire test plan. To change the default test instance lifecycle mode,
simply set the junit.jupiter.testinstance.lifecycle.default configuration parameter to the name
of an enum constant defined in TestInstance.Lifecycle, ignoring case. This can be supplied as a
JVM system property, as a configuration parameter in the LauncherDiscoveryRequest that is passed to
the Launcher, or via the JUnit Platform configuration file (see Configuration Parameters for details).
For example, to set the default test instance lifecycle mode to Lifecycle.PER_CLASS, you can start
your JVM with the following system property.
-Djunit.jupiter.testinstance.lifecycle.default=per_class
Note, however, that setting the default test instance lifecycle mode via the JUnit Platform
configuration file is a more robust solution since the configuration file can be checked into a
version control system along with your project and can therefore be used within IDEs and your
build software.
To set the default test instance lifecycle mode to Lifecycle.PER_CLASS via the JUnit Platform
configuration file, create a file named junit-platform.properties in the root of the class path (e.g.,
src/test/resources) with the following content.
junit.jupiter.testinstance.lifecycle.default = per_class
21

Changing the default test instance lifecycle mode can lead to unpredictable results
and fragile builds if not applied consistently. For example, if the build configures

"

"per-class" semantics as the default but tests in the IDE are executed using "permethod" semantics, that can make it difficult to debug errors that occur on the
build server. It is therefore recommended to change the default in the JUnit
Platform configuration file instead of via a JVM system property.

3.10. Nested Tests
Nested tests give the test writer more capabilities to express the relationship among several group
of tests. HereÕs an elaborate example.
Nested test suite for testing a stack

import
import
import
import

static
static
static
static

org.junit.jupiter.api.Assertions.assertEquals;
org.junit.jupiter.api.Assertions.assertFalse;
org.junit.jupiter.api.Assertions.assertThrows;
org.junit.jupiter.api.Assertions.assertTrue;

import java.util.EmptyStackException;
import java.util.Stack;
import
import
import
import

org.junit.jupiter.api.BeforeEach;
org.junit.jupiter.api.DisplayName;
org.junit.jupiter.api.Nested;
org.junit.jupiter.api.Test;

@DisplayName("A stack")
class TestingAStackDemo {
Ê

Stack stack;

Ê
Ê
Ê
Ê
Ê

@Test
@DisplayName("is instantiated with new Stack()")
void isInstantiatedWithNew() {
new Stack<>();
}

Ê
Ê
Ê

@Nested
@DisplayName("when new")
class WhenNew {

Ê
Ê
Ê
Ê

@BeforeEach
void createNewStack() {
stack = new Stack<>();
}

Ê
Ê
Ê

@Test
@DisplayName("is empty")
void isEmpty() {

22

Ê
Ê

assertTrue(stack.isEmpty());
}

Ê
Ê
Ê
Ê
Ê

@Test
@DisplayName("throws EmptyStackException when popped")
void throwsExceptionWhenPopped() {
assertThrows(EmptyStackException.class, () -> stack.pop());
}

Ê
Ê
Ê
Ê
Ê

@Test
@DisplayName("throws EmptyStackException when peeked")
void throwsExceptionWhenPeeked() {
assertThrows(EmptyStackException.class, () -> stack.peek());
}

Ê
Ê
Ê

@Nested
@DisplayName("after pushing an element")
class AfterPushing {

Ê

String anElement = "an element";

Ê
Ê
Ê
Ê

@BeforeEach
void pushAnElement() {
stack.push(anElement);
}

Ê
Ê
Ê
Ê
Ê

@Test
@DisplayName("it is no longer empty")
void isNotEmpty() {
assertFalse(stack.isEmpty());
}

Ê
Ê
Ê
Ê
Ê
Ê

@Test
@DisplayName("returns the element when popped and is empty")
void returnElementWhenPopped() {
assertEquals(anElement, stack.pop());
assertTrue(stack.isEmpty());
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
}

@Test
@DisplayName("returns the element when peeked but remains not empty")
void returnElementWhenPeeked() {
assertEquals(anElement, stack.peek());
assertFalse(stack.isEmpty());
}
}
}

23

Only non-static nested classes (i.e. inner classes) can serve as @Nested test classes.
Nesting can be arbitrarily deep, and those inner classes are considered to be full

#

members of the test class family with one exception: @BeforeAll and @AfterAll
methods do not work by default. The reason is that Java does not allow static
members in inner classes. However, this restriction can be circumvented by
annotating a @Nested test class with @TestInstance(Lifecycle.PER_CLASS) (see Test
Instance Lifecycle).

3.11. Dependency Injection for Constructors and
Methods
In all prior JUnit versions, test constructors or methods were not allowed to have parameters (at
least not with the standard Runner implementations). As one of the major changes in JUnit Jupiter,
both test constructors and methods are now permitted to have parameters. This allows for greater
flexibility and enables Dependency Injection for constructors and methods.
ParameterResolver defines the API for test extensions that wish to dynamically resolve parameters at
runtime. If a test constructor or a @Test, @TestFactory, @BeforeEach, @AfterEach, @BeforeAll, or
@AfterAll method accepts a parameter, the parameter must be resolved at runtime by a registered
ParameterResolver.
There are currently three built-in resolvers that are registered automatically.
¥ TestInfoParameterResolver:

if

a

method

parameter

is

of

type

TestInfo,

the

TestInfoParameterResolver will supply an instance of TestInfo corresponding to the current test
as the value for the parameter. The TestInfo can then be used to retrieve information about the
current test such as the testÕs display name, the test class, the test method, or associated tags.
The display name is either a technical name, such as the name of the test class or test method,
or a custom name configured via @DisplayName.
TestInfo acts as a drop-in replacement for the TestName rule from JUnit 4. The following
demonstrates how to have TestInfo injected into a test constructor, @BeforeEach method, and
@Test method.

24

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;
import
import
import
import
import

org.junit.jupiter.api.BeforeEach;
org.junit.jupiter.api.DisplayName;
org.junit.jupiter.api.Tag;
org.junit.jupiter.api.Test;
org.junit.jupiter.api.TestInfo;

@DisplayName("TestInfo Demo")
class TestInfoDemo {
Ê
Ê
Ê

TestInfoDemo(TestInfo testInfo) {
assertEquals("TestInfo Demo", testInfo.getDisplayName());
}

Ê
Ê
Ê
Ê
Ê

@BeforeEach
void init(TestInfo testInfo) {
String displayName = testInfo.getDisplayName();
assertTrue(displayName.equals("TEST 1") || displayName.equals("test2()"));
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
@DisplayName("TEST 1")
@Tag("my-tag")
void test1(TestInfo testInfo) {
assertEquals("TEST 1", testInfo.getDisplayName());
assertTrue(testInfo.getTags().contains("my-tag"));
}

Ê
Ê
Ê

@Test
void test2() {
}

}
¥ RepetitionInfoParameterResolver: if a method parameter in a @RepeatedTest, @BeforeEach, or
@AfterEach method is of type RepetitionInfo, the RepetitionInfoParameterResolver will supply an
instance of RepetitionInfo. RepetitionInfo can then be used to retrieve information about the
current repetition and the total number of repetitions for the corresponding @RepeatedTest.
Note, however, that RepetitionInfoParameterResolver is not registered outside the context of a
@RepeatedTest. See Repeated Test Examples.
¥ TestReporterParameterResolver:

if

a

method

parameter

is

of

type

TestReporter,

the

TestReporterParameterResolver will supply an instance of TestReporter. The TestReporter can be
used to publish additional data about the current test run. The data can be consumed through
TestExecutionListener.reportingEntryPublished() and thus be viewed by IDEs or included in
reports.
In JUnit Jupiter you should use TestReporter where you used to print information to stdout or
25

stderr in JUnit 4. Using @RunWith(JUnitPlatform.class) will even output all reported entries to
stdout.

class TestReporterDemo {
Ê
Ê
Ê
Ê

@Test
void reportSingleValue(TestReporter testReporter) {
testReporter.publishEntry("a status message");
}

Ê
Ê
Ê
Ê

@Test
void reportKeyValuePair(TestReporter testReporter) {
testReporter.publishEntry("a key", "a value");
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
void reportMultipleKeyValuePairs(TestReporter testReporter) {
testReporter.publishEntry(
Map.of(
"user name", "dk38",
"award year", "1974"
));
}

}

#

Other parameter resolvers must be explicitly enabled by registering appropriate
extensions via @ExtendWith.

Check out the RandomParametersExtension for an example of a custom ParameterResolver. While not
intended to be production-ready, it demonstrates the simplicity and expressiveness of both the
extension model and the parameter resolution process. MyRandomParametersTest demonstrates how
to inject random values into @Test methods.

26

@ExtendWith(RandomParametersExtension.class)
class MyRandomParametersTest {
Ê
Ê
Ê
Ê

@Test
void injectsInteger(@Random int i, @Random int j) {
assertNotEquals(i, j);
}

Ê
Ê
Ê
Ê

@Test
void injectsDouble(@Random double d) {
assertEquals(0.0, d, 1.0);
}

}
For real-world use cases, check out the source code for the MockitoExtension and the
SpringExtension.

3.12. Test Interfaces and Default Methods
JUnit

Jupiter

allows

@Test,

@RepeatedTest,

@ParameterizedTest,

@TestFactory,

@TestTemplate,

@BeforeEach, and @AfterEach to be declared on interface default methods. @BeforeAll and @AfterAll
can either be declared on static methods in a test interface or on interface default methods if the
test interface or test class is annotated with @TestInstance(Lifecycle.PER_CLASS) (see Test Instance
Lifecycle). Here are some examples.

27

@TestInstance(Lifecycle.PER_CLASS)
interface TestLifecycleLogger {
Ê

static final Logger LOG = Logger.getLogger(TestLifecycleLogger.class.getName());

Ê
Ê
Ê
Ê

@BeforeAll
default void beforeAllTests() {
LOG.info("Before all tests");
}

Ê
Ê
Ê
Ê

@AfterAll
default void afterAllTests() {
LOG.info("After all tests");
}

Ê
Ê
Ê
Ê
Ê

@BeforeEach
default void beforeEachTest(TestInfo testInfo) {
LOG.info(() -> String.format("About to execute [%s]",
testInfo.getDisplayName()));
}

Ê
Ê
Ê
Ê
Ê

@AfterEach
default void afterEachTest(TestInfo testInfo) {
LOG.info(() -> String.format("Finished executing [%s]",
testInfo.getDisplayName()));
}

}

interface TestInterfaceDynamicTestsDemo {
Ê
@TestFactory
Ê
default Collection dynamicTestsFromCollection() {
Ê
return Arrays.asList(
Ê
dynamicTest("1st dynamic test in test interface", () -> assertTrue(true)),
Ê
dynamicTest("2nd dynamic test in test interface", () -> assertEquals(4, 2
* 2))
Ê
);
Ê
}
}
@ExtendWith and @Tag can be declared on a test interface so that classes that implement the interface
automatically inherit its tags and extensions. See Before and After Test Execution Callbacks for the
source code of the TimingExtension.

28

@Tag("timed")
@ExtendWith(TimingExtension.class)
interface TimeExecutionLogger {
}
In your test class you can then implement these test interfaces to have them applied.

class TestInterfaceDemo implements TestLifecycleLogger,
Ê
TimeExecutionLogger, TestInterfaceDynamicTestsDemo {
Ê
Ê
Ê
Ê

@Test
void isEqualValue() {
assertEquals(1, 1, "is always equal");
}

}
Running the TestInterfaceDemo results in output similar to the following:

:junitPlatformTest
INFO example.TestLifecycleLogger - Before all tests
INFO example.TestLifecycleLogger - About to execute [dynamicTestsFromCollection()]
INFO example.TimingExtension - Method [dynamicTestsFromCollection] took 13 ms.
INFO example.TestLifecycleLogger - Finished executing [dynamicTestsFromCollection()]
INFO example.TestLifecycleLogger - About to execute [isEqualValue()]
INFO example.TimingExtension - Method [isEqualValue] took 1 ms.
INFO example.TestLifecycleLogger - Finished executing [isEqualValue()]
INFO example.TestLifecycleLogger - After all tests
Test run finished after 190 ms
[
3 containers found
[
0 containers skipped
[
3 containers started
[
0 containers aborted
[
3 containers successful
[
0 containers failed
[
3 tests found
[
0 tests skipped
[
3 tests started
[
0 tests aborted
[
3 tests successful
[
0 tests failed

]
]
]
]
]
]
]
]
]
]
]
]

BUILD SUCCESSFUL
Another possible application of this feature is to write tests for interface contracts. For example,
you can write tests for how implementations of Object.equals or Comparable.compareTo should

29

behave as follows.

public interface Testable {
Ê

T createValue();

}

public interface EqualsContract extends Testable {
Ê

T createNotEqualValue();

Ê
Ê
Ê
Ê
Ê

@Test
default void valueEqualsItself() {
T value = createValue();
assertEquals(value, value);
}

Ê
Ê
Ê
Ê
Ê

@Test
default void valueDoesNotEqualNull() {
T value = createValue();
assertFalse(value.equals(null));
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
default void valueDoesNotEqualDifferentValue() {
T value = createValue();
T differentValue = createNotEqualValue();
assertNotEquals(value, differentValue);
assertNotEquals(differentValue, value);
}

}

30

public interface ComparableContract> extends Testable {
Ê

T createSmallerValue();

Ê
Ê
Ê
Ê
Ê

@Test
default void returnsZeroWhenComparedToItself() {
T value = createValue();
assertEquals(0, value.compareTo(value));
}

Ê
Ê
Ê
Ê
Ê
Ê

@Test
default void returnsPositiveNumberWhenComparedToSmallerValue() {
T value = createValue();
T smallerValue = createSmallerValue();
assertTrue(value.compareTo(smallerValue) > 0);
}

Ê
Ê
Ê
Ê
Ê
Ê

@Test
default void returnsNegativeNumberWhenComparedToLargerValue() {
T value = createValue();
T smallerValue = createSmallerValue();
assertTrue(smallerValue.compareTo(value) < 0);
}

}
In your test class you can then implement both contract interfaces thereby inheriting the
corresponding tests. Of course youÕll have to implement the abstract methods.

class StringTests implements ComparableContract, EqualsContract {
Ê
Ê
Ê
Ê

@Override
public String createValue() {
return "foo";
}

Ê
Ê
Ê
Ê

@Override
public String createSmallerValue() {
return "bar"; // 'b' < 'f' in "foo"
}

Ê
Ê
Ê
Ê

@Override
public String createNotEqualValue() {
return "baz";
}

}

31

#

The above tests are merely meant as examples and therefore not complete.

3.13. Repeated Tests
JUnit Jupiter provides the ability to repeat a test a specified number of times simply by annotating a
method with @RepeatedTest and specifying the total number of repetitions desired. Each invocation
of a repeated test behaves like the execution of a regular @Test method with full support for the
same lifecycle callbacks and extensions.
The following example demonstrates how to declare a test named repeatedTest() that will be
automatically repeated 10 times.

@RepeatedTest(10)
void repeatedTest() {
Ê
// ...
}
In addition to specifying the number of repetitions, a custom display name can be configured for
each repetition via the name attribute of the @RepeatedTest annotation. Furthermore, the display
name can be a pattern composed of a combination of static text and dynamic placeholders. The
following placeholders are currently supported.
¥ {displayName}: display name of the @RepeatedTest method
¥ {currentRepetition}: the current repetition count
¥ {totalRepetitions}: the total number of repetitions
The default display name for a given repetition is generated based on the following pattern:
"repetition {currentRepetition} of {totalRepetitions}". Thus, the display names for individual
repetitions of the previous repeatedTest() example would be: repetition 1 of 10, repetition 2 of
10, etc. If you would like the display name of the @RepeatedTest method included in the name of
each

repetition,

you

can

define

your

own

custom

pattern

or

use

the

predefined

RepeatedTest.LONG_DISPLAY_NAME pattern. The latter is equal to "{displayName} :: repetition
{currentRepetition}

of

{totalRepetitions}" which results in display names for individual

repetitions like repeatedTest() :: repetition 1 of 10, repeatedTest() :: repetition 2 of 10, etc.
In order to retrieve information about the current repetition and the total number of repetitions
programmatically, a developer can choose to have an instance of RepetitionInfo injected into a
@RepeatedTest, @BeforeEach, or @AfterEach method.

3.13.1. Repeated Test Examples
The RepeatedTestsDemo class at the end of this section demonstrates several examples of repeated
tests.
The repeatedTest() method is identical to example from the previous section; whereas,
repeatedTestWithRepetitionInfo() demonstrates how to have an instance of RepetitionInfo injected
into a test to access the total number of repetitions for the current repeated test.

32

The next two methods demonstrate how to include a custom @DisplayName for the @RepeatedTest
method in the display name of each repetition. customDisplayName() combines a custom display
name with a custom pattern and then uses TestInfo to verify the format of the generated display
name. Repeat! is the {displayName} which comes from the @DisplayName declaration, and 1/1 comes
from {currentRepetition}/{totalRepetitions}. In contrast, customDisplayNameWithLongPattern() uses
the aforementioned predefined RepeatedTest.LONG_DISPLAY_NAME pattern.
repeatedTestInGerman() demonstrates the ability to translate display names of repeated tests into
foreign languages!Ñ!in this case German, resulting in names for individual repetitions such as:
Wiederholung 1 von 5, Wiederholung 2 von 5, etc.
Since the beforeEach() method is annotated with @BeforeEach it will get executed before each
repetition of each repeated test. By having the TestInfo and RepetitionInfo injected into the
method, we see that itÕs possible to obtain information about the currently executing repeated test.
Executing RepeatedTestsDemo with the INFO log level enabled results in the following output.

INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:
INFO:

About
About
About
About
About
About
About
About
About
About
About
About
About
About
About
About
About
About
About
About
About
About

to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to
to

execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute
execute

repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition
repetition

1 of 10 for repeatedTest
2 of 10 for repeatedTest
3 of 10 for repeatedTest
4 of 10 for repeatedTest
5 of 10 for repeatedTest
6 of 10 for repeatedTest
7 of 10 for repeatedTest
8 of 10 for repeatedTest
9 of 10 for repeatedTest
10 of 10 for repeatedTest
1 of 5 for repeatedTestWithRepetitionInfo
2 of 5 for repeatedTestWithRepetitionInfo
3 of 5 for repeatedTestWithRepetitionInfo
4 of 5 for repeatedTestWithRepetitionInfo
5 of 5 for repeatedTestWithRepetitionInfo
1 of 1 for customDisplayName
1 of 1 for customDisplayNameWithLongPattern
1 of 5 for repeatedTestInGerman
2 of 5 for repeatedTestInGerman
3 of 5 for repeatedTestInGerman
4 of 5 for repeatedTestInGerman
5 of 5 for repeatedTestInGerman

import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.logging.Logger;
import
import
import
import
import

org.junit.jupiter.api.BeforeEach;
org.junit.jupiter.api.DisplayName;
org.junit.jupiter.api.RepeatedTest;
org.junit.jupiter.api.RepetitionInfo;
org.junit.jupiter.api.TestInfo;

33

class RepeatedTestsDemo {
Ê

private Logger logger = // ...

Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê

@BeforeEach
void beforeEach(TestInfo testInfo, RepetitionInfo repetitionInfo) {
int currentRepetition = repetitionInfo.getCurrentRepetition();
int totalRepetitions = repetitionInfo.getTotalRepetitions();
String methodName = testInfo.getTestMethod().get().getName();
logger.info(String.format("About to execute repetition %d of %d for %s", //
currentRepetition, totalRepetitions, methodName));
}

Ê
Ê
Ê
Ê

@RepeatedTest(10)
void repeatedTest() {
// ...
}

Ê
Ê
Ê
Ê

@RepeatedTest(5)
void repeatedTestWithRepetitionInfo(RepetitionInfo repetitionInfo) {
assertEquals(5, repetitionInfo.getTotalRepetitions());
}

Ê
@RepeatedTest(value = 1, name = "{displayName}
{currentRepetition}/{totalRepetitions}")
Ê
@DisplayName("Repeat!")
Ê
void customDisplayName(TestInfo testInfo) {
Ê
assertEquals(testInfo.getDisplayName(), "Repeat! 1/1");
Ê
}
Ê
Ê
Ê
Ê
Ê

@RepeatedTest(value = 1, name = RepeatedTest.LONG_DISPLAY_NAME)
@DisplayName("Details...")
void customDisplayNameWithLongPattern(TestInfo testInfo) {
assertEquals(testInfo.getDisplayName(), "Details... :: repetition 1 of 1");
}

Ê
@RepeatedTest(value = 5, name = "Wiederholung {currentRepetition} von
{totalRepetitions}")
Ê
void repeatedTestInGerman() {
Ê
// ...
Ê
}
}
When using the ConsoleLauncher with the unicode theme enabled, execution of RepeatedTestsDemo
results in the following output to the console.

34

#$ RepeatedTestsDemo %
& #$ repeatedTest() %
& & #$ repetition 1 of 10 %
& & #$ repetition 2 of 10 %
& & #$ repetition 3 of 10 %
& & #$ repetition 4 of 10 %
& & #$ repetition 5 of 10 %
& & #$ repetition 6 of 10 %
& & #$ repetition 7 of 10 %
& & #$ repetition 8 of 10 %
& & #$ repetition 9 of 10 %
& & '$ repetition 10 of 10 %
& #$ repeatedTestWithRepetitionInfo(RepetitionInfo) %
& & #$ repetition 1 of 5 %
& & #$ repetition 2 of 5 %
& & #$ repetition 3 of 5 %
& & #$ repetition 4 of 5 %
& & '$ repetition 5 of 5 %
& #$ Repeat! %
& & '$ Repeat! 1/1 %
& #$ Details... %
& & '$ Details... :: repetition 1 of 1 %
& '$ repeatedTestInGerman() %
&
#$ Wiederholung 1 von 5 %
&
#$ Wiederholung 2 von 5 %
&
#$ Wiederholung 3 von 5 %
&
#$ Wiederholung 4 von 5 %
&
'$ Wiederholung 5 von 5 %

3.14. Parameterized Tests
Parameterized tests make it possible to run a test multiple times with different arguments. They are
declared just like regular @Test methods but use the @ParameterizedTest annotation instead. In
addition, you must declare at least one source that will provide the arguments for each invocation
and then consume the arguments in the test method.
The following example demonstrates a parameterized test that uses the @ValueSource annotation to
specify a String array as the source of arguments.

@ParameterizedTest
@ValueSource(strings = { "racecar", "radar", "able was I ere I saw elba" })
void palindromes(String candidate) {
Ê
assertTrue(isPalindrome(candidate));
}
When executing the above parameterized test method, each invocation will be reported separately.
For instance, the ConsoleLauncher will print output similar to the following.

35

palindromes(String) %
#$ [1] racecar %
#$ [2] radar %
'$ [3] able was I ere I saw elba %

"

Parameterized tests are currently an experimental feature. Consult the table in
Experimental APIs for details.

3.14.1. Required Setup
In order to use parameterized tests you need to add a dependency on the junit-jupiter-params
artifact. Please refer to Dependency Metadata for details.

3.14.2. Consuming Arguments
Parameterized test methods typically consume arguments directly from the configured source (see
Sources of Arguments) following a one-to-one correlation between argument source index and
method parameter index (see examples in @CsvSource). However, a parameterized test method
may also choose to aggregate arguments from the source into a single object passed to the method
(see Argument Aggregation). Additional arguments may also be provided by a ParameterResolver
(e.g., to obtain an instance of TestInfo, TestReporter, etc.). Specifically, a parameterized test method
must declare formal parameters according to the following rules.
¥ Zero or more indexed arguments must be declared first.
¥ Zero or more aggregators must be declared next.
¥ Zero or more arguments supplied by a ParameterResolver must be declared last.
In this context, an indexed argument is an argument for a given index in the Arguments provided by
an ArgumentsProvider that is passed as an argument to the parameterized method at the same index
in the methodÕs formal parameter list. An aggregator is any parameter of type ArgumentsAccessor or
any parameter annotated with @AggregateWith.

3.14.3. Sources of Arguments
Out of the box, JUnit Jupiter provides quite a few source annotations. Each of the following
subsections provides a brief overview and an example for each of them. Please refer to the JavaDoc
in the org.junit.jupiter.params.provider package for additional information.
@ValueSource
@ValueSource is one of the simplest possible sources. It lets you specify a single array of literal values
and can only be used for providing a single argument per parameterized test invocation.
The following types of literal values are supported by @ValueSource.
¥ short
¥ byte

36

¥ int
¥ long
¥ float
¥ double
¥ char
¥ java.lang.String
¥ java.lang.Class
For example, the following @ParameterizedTest method will be invoked three times, with the values
1, 2, and 3 respectively.

@ParameterizedTest
@ValueSource(ints = { 1, 2, 3 })
void testWithValueSource(int argument) {
Ê
assertTrue(argument > 0 && argument < 4);
}

@EnumSource
@EnumSource provides a convenient way to use Enum constants. The annotation provides an optional
names parameter that lets you specify which constants shall be used. If omitted, all constants will be
used like in the following example.

@ParameterizedTest
@EnumSource(TimeUnit.class)
void testWithEnumSource(TimeUnit timeUnit) {
Ê
assertNotNull(timeUnit);
}

@ParameterizedTest
@EnumSource(value = TimeUnit.class, names = { "DAYS", "HOURS" })
void testWithEnumSourceInclude(TimeUnit timeUnit) {
Ê
assertTrue(EnumSet.of(TimeUnit.DAYS, TimeUnit.HOURS).contains(timeUnit));
}
The @EnumSource annotation also provides an optional mode parameter that enables fine-grained
control over which constants are passed to the test method. For example, you can exclude names
from the enum constant pool or specify regular expressions as in the following examples.

37

@ParameterizedTest
@EnumSource(value = TimeUnit.class, mode = EXCLUDE, names = { "DAYS", "HOURS" })
void testWithEnumSourceExclude(TimeUnit timeUnit) {
Ê
assertFalse(EnumSet.of(TimeUnit.DAYS, TimeUnit.HOURS).contains(timeUnit));
Ê
assertTrue(timeUnit.name().length() > 5);
}

@ParameterizedTest
@EnumSource(value = TimeUnit.class, mode = MATCH_ALL, names = "^(M|N).+SECONDS$")
void testWithEnumSourceRegex(TimeUnit timeUnit) {
Ê
String name = timeUnit.name();
Ê
assertTrue(name.startsWith("M") || name.startsWith("N"));
Ê
assertTrue(name.endsWith("SECONDS"));
}

@MethodSource
@MethodSource allows you to refer to one or more factory methods of the test class or external
classes.
Factory methods within the test class must be static unless the test class is annotated with
@TestInstance(Lifecycle.PER_CLASS); whereas, factory methods in external classes must always be
static. In addition, such factory methods must not accept any arguments.
Each factory method must generate a stream of arguments, and each set of arguments within the
stream will be provided as the physical arguments for individual invocations of the annotated
@ParameterizedTest method. Generally speaking this translates to a Stream of Arguments (i.e.,
Stream); however, the actual concrete return type can take on many forms. In this
context, a "stream" is anything that JUnit can reliably convert into a Stream, such as Stream,
DoubleStream, LongStream, IntStream, Collection, Iterator, Iterable, an array of objects, or an array of
primitives. The "arguments" within the stream can be supplied as an instance of Arguments, an array
of objects (e.g., Object[]), or a single value if the parameterized test method accepts a single
argument.
If you only need a single parameter, you can return a Stream of instances of the parameter type as
demonstrated in the following example.

@ParameterizedTest
@MethodSource("stringProvider")
void testWithSimpleMethodSource(String argument) {
Ê
assertNotNull(argument);
}
static Stream stringProvider() {
Ê
return Stream.of("foo", "bar");
}

38

If you do not explicitly provide a factory method name via @MethodSource, JUnit Jupiter will search
for a factory method that has the same name as the current @ParameterizedTest method by
convention. This is demonstrated in the following example.

@ParameterizedTest
@MethodSource
void testWithSimpleMethodSourceHavingNoValue(String argument) {
Ê
assertNotNull(argument);
}
static Stream testWithSimpleMethodSourceHavingNoValue() {
Ê
return Stream.of("foo", "bar");
}
Streams for primitive types (DoubleStream, IntStream, and LongStream) are also supported as
demonstrated by the following example.

@ParameterizedTest
@MethodSource("range")
void testWithRangeMethodSource(int argument) {
Ê
assertNotEquals(9, argument);
}
static IntStream range() {
Ê
return IntStream.range(0, 20).skip(10);
}
If a parameterized test method declares multiple parameters, you need to return a collection,
stream, or array of Arguments instances or object arrays as shown below (see the JavaDoc for
@MethodSource for further details on supported return types). Note that arguments(ObjectÉ) is a
static factory method defined in the Arguments interface. In addition, Arguments.of(ObjectÉ) may be
used as an alternative to arguments(ObjectÉ).

@ParameterizedTest
@MethodSource("stringIntAndListProvider")
void testWithMultiArgMethodSource(String str, int num, List list) {
Ê
assertEquals(3, str.length());
Ê
assertTrue(num >=1 && num <=2);
Ê
assertEquals(2, list.size());
}
static Stream stringIntAndListProvider() {
Ê
return Stream.of(
Ê
arguments("foo", 1, Arrays.asList("a", "b")),
Ê
arguments("bar", 2, Arrays.asList("x", "y"))
Ê
);
}

39

An external, static factory method can be referenced by providing its fully qualified method name
as demonstrated in the following example.

package example;
import java.util.stream.Stream;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.MethodSource;
class ExternalMethodSourceDemo {
Ê
Ê
Ê
Ê
Ê
}

@ParameterizedTest
@MethodSource("example.StringsProviders#tinyStrings")
void testWithExternalMethodSource(String tinyString) {
// test with tiny string
}

class StringsProviders {
Ê
Ê
Ê
}

static Stream tinyStrings() {
return Stream.of(".", "oo", "OOO");
}

@CsvSource
@CsvSource allows you to express argument lists as comma-separated values (i.e., String literals).

@ParameterizedTest
@CsvSource({ "foo, 1", "bar, 2", "'baz, qux', 3" })
void testWithCsvSource(String first, int second) {
Ê
assertNotNull(first);
Ê
assertNotEquals(0, second);
}
@CsvSource uses a single quote ' as its quote character. See the 'baz, qux' value in the example
above and in the table below. An empty, quoted value '' results in an empty String; whereas, an
entirely empty value is interpreted as a null reference. An ArgumentConversionException is raised if
the target type of a null reference is a primitive type.
Example Input

Resulting Argument List

@CsvSource({ "foo, bar" })

"foo", "bar"

@CsvSource({ "foo, 'baz, qux'" })

"foo", "baz, qux"

@CsvSource({ "foo, ''" })

"foo", ""

40

Example Input

Resulting Argument List

@CsvSource({ "foo, " })

"foo", null

@CsvFileSource
@CsvFileSource lets you use CSV files from the classpath. Each line from a CSV file results in one
invocation of the parameterized test.

@ParameterizedTest
@CsvFileSource(resources = "/two-column.csv", numLinesToSkip = 1)
void testWithCsvFileSource(String first, int second) {
Ê
assertNotNull(first);
Ê
assertNotEquals(0, second);
}
two-column.csv

Country, reference
Sweden, 1
Poland, 2
"United States of America", 3

In contrast to the syntax used in @CsvSource, @CsvFileSource uses a double quote "

#

as the quote character. See the "United States of America" value in the example
above. An empty, quoted value "" results in an empty String; whereas, an entirely
empty value is interpreted as a null reference. An ArgumentConversionException is
raised if the target type of a null reference is a primitive type.

@ArgumentsSource
@ArgumentsSource can be used to specify a custom, reusable ArgumentsProvider. Note that an
implementation of ArgumentsProvider must be declared as either a top-level class or as a static
nested class.

@ParameterizedTest
@ArgumentsSource(MyArgumentsProvider.class)
void testWithArgumentsSource(String argument) {
Ê
assertNotNull(argument);
}

41

public class MyArgumentsProvider implements ArgumentsProvider {
Ê
Ê
Ê
Ê
}

@Override
public Stream provideArguments(ExtensionContext context) {
return Stream.of("foo", "bar").map(Arguments::of);
}

3.14.4. Argument Conversion
Widening Conversion
JUnit

Jupiter

supports

Widening

Primitive

Conversion

for

arguments

supplied

to

a

@ParameterizedTest. For example, a parameterized test annotated with @ValueSource(ints = { 1, 2,
3 }) can be declared to accept not only an argument of type int but also an argument of type long,
float, or double.
Implicit Conversion
To support use cases like @CsvSource, JUnit Jupiter provides a number of built-in implicit type
converters. The conversion process depends on the declared type of each method parameter.
For example, if a @ParameterizedTest declares a parameter of type TimeUnit and the actual type
supplied by the declared source is a String, the string will be automatically converted into the
corresponding TimeUnit enum constant.

@ParameterizedTest
@ValueSource(strings = "SECONDS")
void testWithImplicitArgumentConversion(TimeUnit argument) {
Ê
assertNotNull(argument.name());
}
String instances are currently implicitly converted to the following target types.
Target
Type

Example

boolean/ "true" # true
Boolean
byte/Byt "1" # (byte) 1
e
char/Cha "o" # 'o'
racter
short/Sh "1" # (short) 1
ort
int/Inte "1" # 1
ger

42

Target
Type

Example

long/Lon "1" # 1L
g
float/Fl "1.0" # 1.0f
oat
double/D "1.0" # 1.0d
ouble
Enum
"SECONDS" # TimeUnit.SECONDS
subclass
java.io. "/path/to/file" # new File("/path/to/file")
File
java.lan "java.lang.Integer" # java.lang.Integer.class (use $ for nested classes, e.g.
g.Class "java.lang.Thread$State")
java.lan "byte" # byte.class (primitive types are supported)
g.Class
java.lan "char[]" # char[].class (array types are supported)
g.Class
java.mat "123.456e789" # new BigDecimal("123.456e789")
h.BigDec
imal
java.mat "1234567890123456789" # new BigInteger("1234567890123456789")
h.BigInt
eger
java.net "http://junit.org/" # URI.create("http://junit.org/")
.URI
java.net "http://junit.org/" # new URL("http://junit.org/")
.URL
java.nio "UTF-8" # Charset.forName("UTF-8")
.charset
.Charset
java.nio "/path/to/file" # Paths.get("/path/to/file")
.file.Pa
th
java.tim "1970-01-01T00:00:00Z" # Instant.ofEpochMilli(0)
e.Instan
t
java.tim "2017-03-14T12:34:56.789" # LocalDateTime.of(2017, 3, 14, 12, 34, 56, 789_000_000)
e.LocalD
ateTime
java.tim "2017-03-14" # LocalDate.of(2017, 3, 14)
e.LocalD
ate
java.tim "12:34:56.789" # LocalTime.of(12, 34, 56, 789_000_000)
e.LocalT
ime
java.tim "2017-03-14T12:34:56.789Z" # OffsetDateTime.of(2017, 3, 14, 12, 34, 56, 789_000_000,
e.Offset ZoneOffset.UTC)
DateTime
java.tim "12:34:56.789Z" # OffsetTime.of(12, 34, 56, 789_000_000, ZoneOffset.UTC)
e.Offset
Time

43

Target
Type

Example

java.tim "2017-03" # YearMonth.of(2017, 3)
e.YearMo
nth
java.tim "2017" # Year.of(2017)
e.Year
java.tim "2017-03-14T12:34:56.789Z" # ZonedDateTime.of(2017, 3, 14, 12, 34, 56, 789_000_000,
e.ZonedD ZoneOffset.UTC)
ateTime
java.uti "JPY" # Currency.getInstance("JPY")
l.Curren
cy
java.uti "en" # new Locale("en")
l.Locale
java.uti "d043e930-7b3b-48e3-bdbe-5a3ccfb833db" # UUID.fromString("d043e930-7b3b-48e3-bdbel.UUID
5a3ccfb833db")
Fallback String-to-Object Conversion

In addition to implicit conversion from strings to the target types listed in the above table, JUnit
Jupiter also provides a fallback mechanism for automatic conversion from a String to a given target
type if the target type declares exactly one suitable factory method or a factory constructor as
defined below.
¥ factory method: a non-private, static method declared in the target type that accepts a single
String argument and returns an instance of the target type. The name of the method can be
arbitrary and need not follow any particular convention.
¥ factory constructor: a non-private constructor in the target type that accepts a single String
argument. Note that the target type must be declared as either a top-level class or as a static
nested class.

#

If multiple factory methods are discovered, they will be ignored. If a factory
method and a factory constructor are discovered, the factory method will be used
instead of the constructor.

For example, in the following @ParameterizedTest method, the Book argument will be created by
invoking the Book.fromTitle(String) factory method and passing "42 Cats" as the title of the book.

@ParameterizedTest
@ValueSource(strings = "42 Cats")
void testWithImplicitFallbackArgumentConversion(Book book) {
Ê
assertEquals("42 Cats", book.getTitle());
}

44

public class Book {
Ê

private final String title;

Ê
Ê
Ê

private Book(String title) {
this.title = title;
}

Ê
Ê
Ê

public static Book fromTitle(String title) {
return new Book(title);
}

Ê
Ê
Ê
}

public String getTitle() {
return this.title;
}

Explicit Conversion
Instead of relying on implicit argument conversion you may explicitly specify an ArgumentConverter
to use for a certain parameter using the @ConvertWith annotation like in the following example. Note
that an implementation of ArgumentConverter must be declared as either a top-level class or as a
static nested class.

@ParameterizedTest
@EnumSource(TimeUnit.class)
void testWithExplicitArgumentConversion(
Ê
@ConvertWith(ToStringArgumentConverter.class) String argument) {
Ê
}

assertNotNull(TimeUnit.valueOf(argument));

public class ToStringArgumentConverter extends SimpleArgumentConverter {
Ê
Ê
Ê
Ê
Ê
}

@Override
protected Object convert(Object source, Class targetType) {
assertEquals(String.class, targetType, "Can only convert to String");
return String.valueOf(source);
}

Explicit argument converters are meant to be implemented by test and extension authors. Thus,
junit-jupiter-params only provides a single explicit argument converter that may also serve as a
reference implementation: JavaTimeArgumentConverter. It is used via the composed annotation
JavaTimeConversionPattern.

45

@ParameterizedTest
@ValueSource(strings = { "01.01.2017", "31.12.2017" })
void testWithExplicitJavaTimeConverter(
Ê
@JavaTimeConversionPattern("dd.MM.yyyy") LocalDate argument) {
Ê
}

assertEquals(2017, argument.getYear());

3.14.5. Argument Aggregation
By default, each argument provided to a @ParameterizedTest method corresponds to a single method
parameter. Consequently, argument sources which are expected to supply a large number of
arguments can lead to large method signatures.
In such cases, an ArgumentsAccessor can be used instead of multiple parameters. Using this API, you
can access the provided arguments through a single argument passed to your test method. In
addition, type conversion is supported as discussed in Implicit Conversion.

@ParameterizedTest
@CsvSource({
Ê
"Jane, Doe, F, 1990-05-20",
Ê
"John, Doe, M, 1990-10-22"
})
void testWithArgumentsAccessor(ArgumentsAccessor arguments) {
Ê
Person person = new Person(arguments.getString(0),
Ê
arguments.getString(1),
Ê
arguments.get(2, Gender.class),
Ê
arguments.get(3, LocalDate.class));
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
}

if (person.getFirstName().equals("Jane")) {
assertEquals(Gender.F, person.getGender());
}
else {
assertEquals(Gender.M, person.getGender());
}
assertEquals("Doe", person.getLastName());
assertEquals(1990, person.getDateOfBirth().getYear());

An instance of ArgumentsAccessor is automatically injected into any parameter of type
ArgumentsAccessor.
Custom Aggregators
Apart from direct access to a @ParameterizedTest methodÕs arguments using an ArgumentsAccessor,
JUnit Jupiter also supports the usage of custom, reusable aggregators.
To use a custom aggregator simply implement the ArgumentsAggregator interface and register it via

46

the @AggregateWith annotation on a compatible parameter in the @ParameterizedTest method. The
result of the aggregation will then be provided as an argument for the corresponding parameter
when the parameterized test is invoked. Note that an implementation of ArgumentsAggregator must
be declared as either a top-level class or as a static nested class.

@ParameterizedTest
@CsvSource({
Ê
"Jane, Doe, F, 1990-05-20",
Ê
"John, Doe, M, 1990-10-22"
})
void testWithArgumentsAggregator(@AggregateWith(PersonAggregator.class) Person person)
{
Ê
// perform assertions against person
}

public class PersonAggregator implements ArgumentsAggregator {
Ê
@Override
Ê
public Person aggregateArguments(ArgumentsAccessor arguments, ParameterContext
context) {
Ê
return new Person(arguments.getString(0),
Ê
arguments.getString(1),
Ê
arguments.get(2, Gender.class),
Ê
arguments.get(3, LocalDate.class));
Ê
}
}
If you find yourself repeatedly declaring @AggregateWith(MyTypeAggregator.class) for multiple
parameterized test methods across your codebase, you may wish to create a custom composed
annotation

such

as

@CsvToMyType

that

is

meta-annotated

with

@AggregateWith(MyTypeAggregator.class). The following example demonstrates this in action with a
custom @CsvToPerson annotation.

@ParameterizedTest
@CsvSource({
Ê
"Jane, Doe, F, 1990-05-20",
Ê
"John, Doe, M, 1990-10-22"
})
void testWithCustomAggregatorAnnotation(@CsvToPerson Person person) {
Ê
// perform assertions against person
}

47

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
@AggregateWith(PersonAggregator.class)
public @interface CsvToPerson {
}

3.14.6. Customizing Display Names
By default, the display name of a parameterized test invocation contains the invocation index and
the String representation of all arguments for that specific invocation. However, you can customize
invocation display names via the name attribute of the @ParameterizedTest annotation like in the
following example.

@DisplayName("Display name of container")
@ParameterizedTest(name = "{index} ==> first=''{0}'', second={1}")
@CsvSource({ "foo, 1", "bar, 2", "'baz, qux', 3" })
void testWithCustomDisplayNames(String first, int second) {
}
When executing the above method using the ConsoleLauncher you will see output similar to the
following.

Display name of container %
#$ 1 ==> first='foo', second=1 %
#$ 2 ==> first='bar', second=2 %
'$ 3 ==> first='baz, qux', second=3 %
The following placeholders are supported within custom display names.
Placeholder

Description

{index}

the current invocation index (1-based)

{arguments}

the complete, comma-separated arguments list

{0}, {1}, É

an individual argument

3.14.7. Lifecycle and Interoperability
Each invocation of a parameterized test has the same lifecycle as a regular @Test method. For
example, @BeforeEach methods will be executed before each invocation. Similar to Dynamic Tests,
invocations will appear one by one in the test tree of an IDE. You may at will mix regular @Test
methods and @ParameterizedTest methods within the same test class.
You may use ParameterResolver extensions with @ParameterizedTest methods. However, method
parameters that are resolved by argument sources need to come first in the argument list. Since a
test class may contain regular tests as well as parameterized tests with different parameter lists,
values from argument sources are not resolved for lifecycle methods (e.g. @BeforeEach) and test

48

class constructors.

@BeforeEach
void beforeEach(TestInfo testInfo) {
Ê
// ...
}
@ParameterizedTest
@ValueSource(strings = "foo")
void testWithRegularParameterResolver(String argument, TestReporter testReporter) {
Ê
testReporter.publishEntry("argument", argument);
}
@AfterEach
void afterEach(TestInfo testInfo) {
Ê
// ...
}

3.15. Test Templates
A @TestTemplate method is not a regular test case but rather a template for test cases. As such, it is
designed to be invoked multiple times depending on the number of invocation contexts returned by
the

registered

providers.

Thus,

it

must

be

used

in

conjunction

with

a

registered

TestTemplateInvocationContextProvider extension. Each invocation of a test template method
behaves like the execution of a regular @Test method with full support for the same lifecycle
callbacks and extensions. Please refer to Providing Invocation Contexts for Test Templates for usage
examples.

3.16. Dynamic Tests
The standard @Test annotation in JUnit Jupiter described in Annotations is very similar to the @Test
annotation in JUnit 4. Both describe methods that implement test cases. These test cases are static in
the sense that they are fully specified at compile time, and their behavior cannot be changed by
anything happening at runtime. Assumptions provide a basic form of dynamic behavior but are
intentionally rather limited in their expressiveness.
In addition to these standard tests a completely new kind of test programming model has been
introduced in JUnit Jupiter. This new kind of test is a dynamic test which is generated at runtime by
a factory method that is annotated with @TestFactory.
In contrast to @Test methods, a @TestFactory method is not itself a test case but rather a factory for
test cases. Thus, a dynamic test is the product of a factory. Technically speaking, a @TestFactory
method must return a Stream, Collection, Iterable, Iterator, or array of DynamicNode instances.
Instantiable subclasses of DynamicNode are DynamicContainer and DynamicTest. DynamicContainer
instances are composed of a display name and a list of dynamic child nodes, enabling the creation
of arbitrarily nested hierarchies of dynamic nodes. DynamicTest instances will be executed lazily,
enabling dynamic and even non-deterministic generation of test cases.

49

Any Stream returned by a @TestFactory will be properly closed by calling stream.close(), making it
safe to use a resource such as Files.lines().
As with @Test methods, @TestFactory methods must not be private or static and may optionally
declare parameters to be resolved by ParameterResolvers.
A DynamicTest is a test case generated at runtime. It is composed of a display name and an
Executable. Executable is a @FunctionalInterface which means that the implementations of dynamic
tests can be provided as lambda expressions or method references.
Dynamic Test Lifecycle

The execution lifecycle of a dynamic test is quite different than it is for a standard
@Test case. Specifically, there are no lifecycle callbacks for individual dynamic

"

tests.

This

means

that

@BeforeEach

and

@AfterEach

methods

and

their

corresponding extension callbacks are executed for the @TestFactory method but
not for each dynamic test. In other words, if you access fields from the test instance
within a lambda expression for a dynamic test, those fields will not be reset by
callback methods or extensions between the execution of individual dynamic tests
generated by the same @TestFactory method.

As of JUnit Jupiter 5.3.2, dynamic tests must always be created by factory methods; however, this
might be complemented by a registration facility in a later release.

"

Dynamic tests are currently an experimental feature. Consult the table in
Experimental APIs for details.

3.16.1. Dynamic Test Examples
The following DynamicTestsDemo class demonstrates several examples of test factories and dynamic
tests.
The first method returns an invalid return type. Since an invalid return type cannot be detected at
compile time, a JUnitException is thrown when it is detected at runtime.
The next five methods are very simple examples that demonstrate the generation of a Collection,
Iterable, Iterator, or Stream of DynamicTest instances. Most of these examples do not really exhibit
dynamic behavior but merely demonstrate the supported return types in principle. However,
dynamicTestsFromStream() and dynamicTestsFromIntStream() demonstrate how easy it is to generate
dynamic tests for a given set of strings or a range of input numbers.
The next method is truly dynamic in nature. generateRandomNumberOfTests() implements an Iterator
that generates random numbers, a display name generator, and a test executor and then provides
all

three

to

DynamicTest.stream().

Although

the

non-deterministic

behavior

of

generateRandomNumberOfTests() is of course in conflict with test repeatability and should thus be
used with care, it serves to demonstrate the expressiveness and power of dynamic tests.
The last method generates a nested hierarchy of dynamic tests utilizing DynamicContainer.

50

import
import
import
import
import
import

static
static
static
static
static
static

org.junit.jupiter.api.Assertions.assertEquals;
org.junit.jupiter.api.Assertions.assertFalse;
org.junit.jupiter.api.Assertions.assertNotNull;
org.junit.jupiter.api.Assertions.assertTrue;
org.junit.jupiter.api.DynamicContainer.dynamicContainer;
org.junit.jupiter.api.DynamicTest.dynamicTest;

import
import
import
import
import
import
import
import

java.util.Arrays;
java.util.Collection;
java.util.Iterator;
java.util.List;
java.util.Random;
java.util.function.Function;
java.util.stream.IntStream;
java.util.stream.Stream;

import
import
import
import
import

org.junit.jupiter.api.DynamicNode;
org.junit.jupiter.api.DynamicTest;
org.junit.jupiter.api.Tag;
org.junit.jupiter.api.TestFactory;
org.junit.jupiter.api.function.ThrowingConsumer;

class DynamicTestsDemo {
Ê
Ê
Ê
Ê
Ê

// This will result in a JUnitException!
@TestFactory
List dynamicTestsWithInvalidReturnType() {
return Arrays.asList("Hello");
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê

@TestFactory
Collection dynamicTestsFromCollection() {
return Arrays.asList(
dynamicTest("1st dynamic test", () -> assertTrue(true)),
dynamicTest("2nd dynamic test", () -> assertEquals(4, 2 * 2))
);
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê

@TestFactory
Iterable dynamicTestsFromIterable() {
return Arrays.asList(
dynamicTest("3rd dynamic test", () -> assertTrue(true)),
dynamicTest("4th dynamic test", () -> assertEquals(4, 2 * 2))
);
}

Ê
Ê
Ê
Ê
Ê

@TestFactory
Iterator dynamicTestsFromIterator() {
return Arrays.asList(
dynamicTest("5th dynamic test", () -> assertTrue(true)),
dynamicTest("6th dynamic test", () -> assertEquals(4, 2 * 2))

51

Ê
Ê

}

Ê
Ê
Ê
Ê
Ê
Ê
Ê

@TestFactory
DynamicTest[] dynamicTestsFromArray() {
return new DynamicTest[] {
dynamicTest("7th dynamic test", () -> assertTrue(true)),
dynamicTest("8th dynamic test", () -> assertEquals(4, 2 * 2))
};
}

Ê
Ê
Ê
Ê
Ê

@TestFactory
Stream dynamicTestsFromStream() {
return Stream.of("A", "B", "C")
.map(str -> dynamicTest("test" + str, () -> { /* ... */ }));
}

Ê
Ê
Ê
Ê
Ê
Ê

@TestFactory
Stream dynamicTestsFromIntStream() {
// Generates tests for the first 10 even integers.
return IntStream.iterate(0, n -> n + 2).limit(10)
.mapToObj(n -> dynamicTest("test" + n, () -> assertTrue(n % 2 == 0)));
}

Ê
Ê

@TestFactory
Stream generateRandomNumberOfTests() {

Ê
Ê
Ê

).iterator();

// Generates random positive integers between 0 and 100 until
// a number evenly divisible by 7 is encountered.
Iterator inputGenerator = new Iterator<>() {

Ê
Ê

Random random = new Random();
int current;

Ê
Ê
Ê
Ê
Ê

@Override
public boolean hasNext() {
current = random.nextInt(100);
return current % 7 != 0;
}

Ê
Ê
Ê
Ê
Ê

@Override
public Integer next() {
return current;
}
};

Ê
Ê

// Generates display names like: input:5, input:37, input:85, etc.
Function displayNameGenerator = (input) -> "input:" + input;

Ê
Ê

// Executes tests based on the current input value.
ThrowingConsumer testExecutor = (input) -> assertTrue(input % 7 != 0

52

);
Ê
Ê
Ê

// Returns a stream of dynamic tests.
return DynamicTest.stream(inputGenerator, displayNameGenerator, testExecutor);
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê

@TestFactory
Stream dynamicTestsWithContainers() {
return Stream.of("A", "B", "C")
.map(input -> dynamicContainer("Container " + input, Stream.of(
dynamicTest("not null", () -> assertNotNull(input)),
dynamicContainer("properties", Stream.of(
dynamicTest("length > 0", () -> assertTrue(input.length() > 0)),
dynamicTest("not empty", () -> assertFalse(input.isEmpty()))
))
)));
}

}

3.17. Parallel Execution
By default, JUnit Jupiter tests are run sequentially in a single thread. Running tests in parallel, e.g.
to speed up execution, is available as an opt-in feature since version 5.3. To enable parallel
execution, simply set the junit.jupiter.execution.parallel.enabled configuration parameter to
true, e.g. in junit-platform.properties (see Configuration Parameters for other options).
Once enabled, the JUnit Jupiter engine will execute tests on all levels of the test tree fully in parallel
according to the provided configuration while observing the declarative synchronization
mechanisms. Please note that the Capturing Standard Output/Error feature needs to enabled
separately.

"

Parallel test execution is currently an experimental feature. YouÕre invited to give it
a try and provide feedback to the JUnit team so they can improve and eventually
promote this feature.

3.17.1. Configuration
Properties like the desired parallelism and the maximum pool size can be configured using a
ParallelExecutionConfigurationStrategy. The JUnit Platform provides two implementations out of
the box: dynamic and fixed. Alternatively, you may implement a custom strategy.
To select a strategy, simply set the junit.jupiter.execution.parallel.config.strategy configuration
parameter to one of the following options:
dynamic
Computes the desired parallelism based on the number of available processors/cores multiplied
by

the

junit.jupiter.execution.parallel.config.dynamic.factor

configuration

parameter

(defaults to 1).
53

fixed
Uses the mandatory junit.jupiter.execution.parallel.config.fixed.parallelism configuration
parameter as desired parallelism.
custom
Allows to specify a custom ParallelExecutionConfigurationStrategy implementation via the
mandatory junit.jupiter.execution.parallel.config.custom.class configuration parameter to
determine the desired configuration.
If no configuration strategy is set, JUnit Jupiter uses the dynamic configuration strategy with a factor
of 1, i.e. the desired parallelism will equal the number of available processors/cores.

3.17.2. Synchronization
In the org.junit.jupiter.api.parallel package, JUnit Jupiter provides two annotation-based
declarative mechanisms to change the execution mode and allow for synchronization when using
shared resources in different tests.
If parallel execution is enabled, all classes and methods are executed concurrently by default. You
can change the execution mode for the annotated element and its subelements (if any) by using the
@Execution annotation. The following two modes are available:
SAME_THREAD
Force execution in the same thread used by the parent. For example, when used on a test
method, the test method will be executed in the same thread as any @BeforeAll or @AfterAll
methods of the containing test class.
CONCURRENT
Execute concurrently unless a resource constraint forces execution in the same thread.
In addition, the @ResourceLock annotation allows to declare that a test class or method uses a
specific shared resource that requires synchronized access to ensure reliable test execution.
If the tests in the following example were run in parallel they would be flaky, i.e. sometimes pass
and other times fail, because of the inherent race condition of writing and then reading the same
system property.

54

@Execution(CONCURRENT)
class SharedResourcesDemo {
Ê

private Properties backup;

Ê
Ê
Ê
Ê
Ê

@BeforeEach
void backup() {
backup = new Properties();
backup.putAll(System.getProperties());
}

Ê
Ê
Ê
Ê

@AfterEach
void restore() {
System.setProperties(backup);
}

Ê
Ê
Ê
Ê
Ê

@Test
@ResourceLock(value = SYSTEM_PROPERTIES, mode = READ)
void customPropertyIsNotSetByDefault() {
assertNull(System.getProperty("my.prop"));
}

Ê
Ê
Ê
Ê
Ê
Ê

@Test
@ResourceLock(value = SYSTEM_PROPERTIES, mode = READ_WRITE)
void canSetCustomPropertyToFoo() {
System.setProperty("my.prop", "foo");
assertEquals("foo", System.getProperty("my.prop"));
}

Ê
Ê
Ê
Ê
Ê
Ê
}

@Test
@ResourceLock(value = SYSTEM_PROPERTIES, mode = READ_WRITE)
void canSetCustomPropertyToBar() {
System.setProperty("my.prop", "bar");
assertEquals("bar", System.getProperty("my.prop"));
}

When access to shared resources is declared using this annotation, the JUnit Jupiter engine uses this
information to ensure that no conflicting tests are run in parallel.
In addition to the string that uniquely identifies the used resource, you may specify an access mode.
Two tests that require READ access to a resource may run in parallel with each other but not while
any other test that requires READ_WRITE access is running.

4. Running Tests

55

4.1. IDE Support
4.1.1. IntelliJ IDEA
IntelliJ IDEA supports running tests on the JUnit Platform since version 2016.2. For details please
see the post on the IntelliJ IDEA blog. Note, however, that it is recommended to use IDEA 2017.3 or
newer since these newer versions of IDEA will download the following JARs automatically based on
the API version used in the project: junit-platform-launcher, junit-jupiter-engine, and junitvintage-engine.
IntelliJ IDEA releases prior to IDEA 2017.3 bundle specific versions of JUnit 5. Thus,

"

if you want to use a newer version of JUnit Jupiter, execution of tests within the
IDE might fail due to version conflicts. In such cases, please follow the instructions
below to use a newer version of JUnit 5 than the one bundled with IntelliJ IDEA.

In order to use a different JUnit 5 version (e.g., 5.3.2), you may need to include the corresponding
versions of the junit-platform-launcher, junit-jupiter-engine, and junit-vintage-engine JARs in the
classpath.
Additional Gradle Dependencies

// Only needed to run tests in a version of IntelliJ IDEA that bundles older versions
testRuntime("org.junit.platform:junit-platform-launcher:1.3.2")
testRuntime("org.junit.jupiter:junit-jupiter-engine:5.3.2")
testRuntime("org.junit.vintage:junit-vintage-engine:5.3.2")
Additional Maven Dependencies



Ê
org.junit.platform
Ê
junit-platform-launcher
Ê
1.3.2
Ê
test


Ê
org.junit.jupiter
Ê
junit-jupiter-engine
Ê
5.3.2
Ê
test


Ê
org.junit.vintage
Ê
junit-vintage-engine
Ê
5.3.2
Ê
test


56

4.1.2. Eclipse
Eclipse IDE offers support for the JUnit Platform since the Eclipse Oxygen.1a (4.7.1a) release.
For more information on using JUnit 5 in Eclipse consult the official Eclipse support for JUnit 5
section of the Eclipse Project Oxygen.1a (4.7.1a) - New and Noteworthy documentation.

4.1.3. Other IDEs
At the time of this writing, there is no direct support for running tests on the JUnit Platform within
IDEs other than IntelliJ IDEA and Eclipse. However, the JUnit team provides two intermediate
solutions so that you can go ahead and try out JUnit 5 within your IDE today. You can use the
Console Launcher manually or execute tests with a JUnit 4 based Runner.

4.2. Build Support
4.2.1. Gradle
Starting with version 4.6, Gradle provides native support for executing tests on the JUnit Platform.
To enable it, you just need to specify useJUnitPlatform() within a test task declaration in
build.gradle:

test {
Ê
useJUnitPlatform()
}
Filtering by tags or engines is also supported:

test {
Ê
useJUnitPlatform {
Ê
includeTags 'fast', 'smoke & feature-a'
Ê
// excludeTags 'slow', 'ci'
Ê
includeEngines 'junit-jupiter'
Ê
// excludeEngines 'junit-vintage'
Ê
}
}
Please refer to the official Gradle documentation for a comprehensive list of options.
The JUnit Platform Gradle Plugin has been discontinued

"

The very basic junit-platform-gradle-plugin developed by the JUnit team was
deprecated in JUnit Platform 1.2 and discontinued in 1.3. Please switch to GradleÕs
standard test task.

57

Configuration Parameters
The standard Gradle test task currently does not provide a dedicated DSL to set JUnit Platform
configuration parameters to influence test discovery and execution. However, you can provide
configuration parameters within the build script via system properties (as shown below) or via the
junit-platform.properties file.

test {
Ê
// ...
Ê
systemProperty 'junit.jupiter.conditions.deactivate', '*'
Ê
systemProperties = [
Ê
'junit.jupiter.extensions.autodetection.enabled': 'true',
Ê
'junit.jupiter.testinstance.lifecycle.default': 'per_class'
Ê
]
Ê
// ...
}

Configuring Test Engines
In order to run any tests at all, a TestEngine implementation must be on the classpath.
To configure support for JUnit Jupiter based tests, configure a testCompile dependency on the JUnit
Jupiter API and a testRuntime dependency on the JUnit Jupiter TestEngine implementation similar to
the following.

dependencies {
Ê
testCompile("org.junit.jupiter:junit-jupiter-api:5.3.2")
Ê
testRuntime("org.junit.jupiter:junit-jupiter-engine:5.3.2")
}
The JUnit Platform can run JUnit 4 based tests as long as you configure a testCompile dependency
on JUnit 4 and a testRuntime dependency on the JUnit Vintage TestEngine implementation similar to
the following.

dependencies {
Ê
testCompile("junit:junit:4.12")
Ê
testRuntime("org.junit.vintage:junit-vintage-engine:5.3.2")
}

Configuring Logging (optional)
JUnit uses the Java Logging APIs in the java.util.logging package (a.k.a. JUL) to emit warnings and
debug information. Please refer to the official documentation of LogManager for configuration
options.
Alternatively, itÕs possible to redirect log messages to other logging frameworks such as Log4j or
Logback. To use a logging framework that provides a custom implementation of LogManager, set the

58

java.util.logging.manager system property to the fully qualified class name of the LogManager
implementation to use. The example below demonstrates how to configure Log4jÊ2.x (see Log4j JDK
Logging Adapter for details).

test {
Ê
systemProperty 'java.util.logging.manager',
'org.apache.logging.log4j.jul.LogManager'
}
Other logging frameworks provide different means to redirect messages logged using
java.util.logging. For example, for Logback you can use the JUL to SLF4J Bridge by adding an
additional dependency to the runtime classpath.

4.2.2. Maven

#

The custom junit-platform-surefire-provider, which was originally developed by
the JUnit team, has been deprecated and is scheduled to be removed in JUnit
Platform 1.4. Please use Maven SurefireÕs native support instead.

Starting with version 2.22.0, Maven Surefire provides native support for executing tests on the JUnit
Platform. The pom.xml file in the junit5-jupiter-starter-maven project demonstrates how to use it
and can serve as a starting point for configuring your Maven build.
Configuring Test Engines
In order to have Maven Surefire run any tests at all, at least one TestEngine implementation must
be added to the test classpath.
To configure support for JUnit Jupiter based tests, configure test scoped dependencies on the JUnit
Jupiter API and the JUnit Jupiter TestEngine implementation similar to the following.

59


Ê

Ê

Ê
maven-surefire-plugin
Ê
2.22.0
Ê

Ê


...

Ê
...
Ê

Ê
org.junit.jupiter
Ê
junit-jupiter-api
Ê
5.3.2
Ê
test
Ê

Ê

Ê
org.junit.jupiter
Ê
junit-jupiter-engine
Ê
5.3.2
Ê
test
Ê

Ê
...

...
Maven Surefire can run JUnit 4 based tests alongside Jupiter tests as long as you configure test
scoped dependencies on JUnit 4 and the JUnit Vintage TestEngine implementation similar to the
following.

60

...

Ê

Ê

Ê
maven-surefire-plugin
Ê
2.22.0
Ê

Ê


...

Ê
...
Ê

Ê
junit
Ê
junit
Ê
4.12
Ê
test
Ê

Ê

Ê
org.junit.vintage
Ê
junit-vintage-engine
Ê
5.3.2
Ê
test
Ê

Ê
...

...

Filtering by Test Class Names
The Maven Surefire Plugin will scan for test classes whose fully qualified names match the
following patterns.
¥ **/Test*.java
¥ **/*Test.java
¥ **/*Tests.java
¥ **/*TestCase.java
Moreover, it will exclude all nested classes (including static member classes) by default.
Note, however, that you can override this default behavior by configuring explicit include and
exclude rules in your pom.xml file. For example, to keep Maven Surefire from excluding static
member classes, you can override its exclude rules as follows.

61

Overriding exclude rules of Maven Surefire

...

Ê

Ê

Ê
maven-surefire-plugin
Ê
2.22.0
Ê

Ê

Ê

Ê

Ê

Ê

Ê


...
Please see the Inclusions and Exclusions of Tests documentation for Maven Surefire for details.
Filtering by Tags
You can filter tests by tags or tag expressions using the following configuration properties.
¥ to include tags or tag expressions, use groups.
¥ to exclude tags or tag expressions, use excludedGroups.

...

Ê

Ê

Ê
maven-surefire-plugin
Ê
2.22.0
Ê

Ê
acceptance | !feature-a
Ê
integration, regression
Ê

Ê

Ê


...

Configuration Parameters
You can set JUnit Platform configuration parameters to influence test discovery and execution by
declaring the configurationParameters property and providing key-value pairs using the Java
Properties file syntax (as shown below) or via the junit-platform.properties file.

62

...

Ê

Ê

Ê
maven-surefire-plugin
Ê
2.22.0
Ê

Ê

Ê

Ê
junit.jupiter.conditions.deactivate = *
Ê
junit.jupiter.extensions.autodetection.enabled = true
Ê
junit.jupiter.testinstance.lifecycle.default = per_class
Ê

Ê

Ê

Ê

Ê


...

4.2.3. Ant
Starting with version 1.10.3 of Ant, a new junitlauncher task has been introduced to provide native
support for launching tests on the JUnit Platform. The junitlauncher task is solely responsible for
launching the JUnit Platform and passing it the selected collection of tests. The JUnit Platform then
delegates to registered test engines to discover and execute the tests.
The junitlauncher task attempts to align as close as possible with native Ant constructs such as
resource collections for allowing users to select the tests that they want executed by test engines.
This gives the task a consistent and natural feel when compared to many other core Ant tasks.
The version of the junitlauncher task shipped in Ant 1.10.3 provides basic, minimal

#

support for launching the JUnit Platform. Additional enhancements (including
support for forking the tests in a separate JVM) will be available in subsequent
releases of Ant.

The build.xml file in the junit5-jupiter-starter-ant project demonstrates how to use it and can
serve as a starting point.
Basic Usage
The following example demonstrates how to configure the junitlauncher task to select a single test
class (i.e., org.myapp.test.MyFirstJUnit5Test).

63


Ê

Ê




Ê

Ê


The test element allows you to specify a single test class that you want to be selected and executed.
The classpath element allows you to specify the classpath to be used to launch the JUnit Platform.
This classpath will also be used to locate test classes that are part of the execution.
The following example demonstrates how to configure the junitlauncher task to select test classes
from multiple locations.


Ê

Ê


....

Ê

Ê

Ê

Ê

Ê

Ê

Ê

Ê

Ê


In the above example, the testclasses element allows you to select multiple test classes that reside
in different locations.
For further details on usage and configuration options please refer to the official Ant
documentation for the junitlauncher task.

4.3. Console Launcher
The ConsoleLauncher is a command-line Java application that lets you launch the JUnit Platform
from the console. For example, it can be used to run JUnit Vintage and JUnit Jupiter tests and print
test execution results to the console.

64

An executable junit-platform-console-standalone-1.3.2.jar with all dependencies included is
published in the central Maven repository under the junit-platform-console-standalone directory.
You can run the standalone ConsoleLauncher as shown below.
java -jar junit-platform-console-standalone-1.3.2.jar 
HereÕs an example of its output:

#$ JUnit Vintage
& '$ example.JUnit4Tests
&
'$ standardJUnit4Test %
'$ JUnit Jupiter
Ê #$ StandardTests
Ê & #$ succeedingTest() %
Ê & '$ skippedTest() ( for demonstration purposes
Ê '$ A special test case
Ê
#$ Custom test name containing spaces %
Ê
#$ !¡!¡"! %
Ê
'$ " %
Test run finished after 64 ms
[
5 containers found
[
0 containers skipped
[
5 containers started
[
0 containers aborted
[
5 containers successful
[
0 containers failed
[
6 tests found
[
1 tests skipped
[
5 tests started
[
0 tests aborted
[
5 tests successful
[
0 tests failed

]
]
]
]
]
]
]
]
]
]
]
]

Exit Code

#

The ConsoleLauncher exits with a status code of 1 if any containers or tests failed. If
no tests are discovered and the --fail-if-no-tests command-line option is
supplied, the ConsoleLauncher exits with a status code of 2. Otherwise the exit code
is 0.

4.3.1. Options
Usage: ConsoleLauncher
modules]
Ê
Ê
Ê
Ê

[-h] [--disable-ansi-colors] [--fail-if-no-tests] [--scan[--scan-classpath[=PATH[;|:PATH...]]]... [--details=MODE]
[--details-theme=THEME] [--reports-dir=DIR]
[--config=KEY=VALUE]... [--exclude-package=PKG]...
[--include-package=PKG]... [-c=CLASS]... [-

65

cp=PATH[;|:PATH...]]...
Ê
[-d=DIR]... [-e=ID]... [-E=ID]... [-f=FILE]... [-m=NAME]...
Ê
[-n=PATTERN]... [-N=PATTERN]... [-o=NAME]... [-p=PKG]...
Ê
[-r=RESOURCE]... [-t=TAG]... [-T=TAG]... [-u=URI]...
Launches the JUnit Platform from the console.
Ê -h, --help
Display help information.
Ê
--disable-ansi-colors Disable ANSI colors in output (not supported by all
terminals).
Ê
--details=MODE
Select an output details mode for when tests are
executed. Use
Ê
one of: none, summary, flat, tree, verbose. If 'none'
is
Ê
selected, then only the summary and test failures are
shown.
Ê
Default: tree.
Ê
--details-theme=THEME Select an output details tree theme for when tests are
executed.
Ê
Use one of: ascii, unicode. Default: unicode.
Ê
-cp, --classpath, --class-path=PATH[;|:PATH...]
Ê
Provide additional classpath entries -- for example, for
adding
Ê
engines and their dependencies. This option can be
repeated.
Ê
--fail-if-no-tests
Fail and return exit status code 2 if no tests are found.
Ê
--reports-dir=DIR
Enable report output into a specified local directory
(will be
Ê
created if it does not exist).
Ê
--scan-modules
EXPERIMENTAL: Scan all resolved modules for test
discovery.
Ê -o, --select-module=NAME
EXPERIMENTAL: Select single module for test discovery.
This
Ê
option can be repeated.
Ê
--scan-classpath, --scan-class-path[=PATH[;|:PATH...]]
Ê
Scan all directories on the classpath or explicit
classpath
Ê
roots. Without arguments, only directories on the
system
Ê
classpath as well as additional classpath entries
supplied via
Ê
-cp (directories and JAR files) are scanned. Explicit
classpath
Ê
roots that are not on the classpath will be silently
ignored.
Ê
This option can be repeated.
Ê -u, --select-uri=URI
Select a URI for test discovery. This option can be
repeated.
Ê -f, --select-file=FILE
Select a file for test discovery. This option can be
repeated.
Ê -d, --select-directory=DIR Select a directory for test discovery. This option can be
Ê
repeated.
Ê -p, --select-package=PKG
Select a package for test discovery. This option can be

66

repeated.
Ê -c, --select-class=CLASS
Select a class for test discovery. This option can be
repeated.
Ê -m, --select-method=NAME
Select a method for test discovery. This option can be
repeated.
Ê -r, --select-resource=RESOURCE
Ê
Select a classpath resource for test discovery. This
option can
Ê
be repeated.
Ê -n, --include-classname=PATTERN
Ê
Provide a regular expression to include only classes
whose fully
Ê
qualified names match. To avoid loading classes
unnecessarily,
Ê
the default pattern only includes class names that
begin with
Ê
"Test" or end with "Test" or "Tests". When this option
is
Ê
repeated, all patterns will be combined using OR
semantics.
Ê
Default: [^(Test.*|.+[.$]Test.*|.*Tests?)$]
Ê -N, --exclude-classname=PATTERN
Ê
Provide a regular expression to exclude those classes
whose fully
Ê
qualified names match. When this option is repeated,
all
Ê
patterns will be combined using OR semantics.
Ê
--include-package=PKG Provide a package to be included in the test run. This
option can
Ê
be repeated.
Ê
--exclude-package=PKG Provide a package to be excluded from the test run. This
option
Ê
can be repeated.
Ê -t, --include-tag=TAG
Provide a tag or tag expression to include only tests
whose tags
Ê
match. When this option is repeated, all patterns will
be
Ê
combined using OR semantics.
Ê -T, --exclude-tag=TAG
Provide a tag or tag expression to exclude those tests
whose tags
Ê
match. When this option is repeated, all patterns will
be
Ê
combined using OR semantics.
Ê -e, --include-engine=ID
Provide the ID of an engine to be included in the test
run. This
Ê
option can be repeated.
Ê -E, --exclude-engine=ID
Provide the ID of an engine to be excluded from the test
run.
Ê
This option can be repeated.
Ê
--config=KEY=VALUE
Set a configuration parameter for test discovery and
execution.

67

Ê

This option can be repeated.

4.3.2. Argument Files (@-files)
On some platforms you may run into system limitations on the length of a command line when
creating a command line with lots of options or with long arguments.
Since version 1.3, the ConsoleLauncher supports argument files, also known as @-files. Argument files
are files that themselves contain arguments to be passed to the command. When the underlying
picocli command line parser encounters an argument beginning with the character @, it expands
the contents of that file into the argument list.
The arguments within a file can be separated by spaces or newlines. If an argument contains
embedded whitespace, the whole argument should be wrapped in double or single quotes!Ñ!for
example, "-f=My Files/Stuff.java".
If the argument file does not exist or cannot be read, the argument will be treated literally and will
not be removed. This will likely result in an "unmatched argument" error message. You can
troubleshoot such errors by executing the command with the picocli.trace system property set to
DEBUG.
Multiple @-files may be specified on the command line. The specified path may be relative to the
current directory or absolute.
You can pass a real parameter with an initial @ character by escaping it with an additional @ symbol.
For example, @@somearg will become @somearg and will not be subject to expansion.

4.4. Using JUnit 4 to run the JUnit Platform
The JUnitPlatform runner is a JUnit 4 based Runner which enables you to run any test whose
programming model is supported on the JUnit Platform in a JUnit 4 environment!Ñ!for example, a
JUnit Jupiter test class.
Annotating a class with @RunWith(JUnitPlatform.class) allows it to be run with IDEs and build
systems that support JUnit 4 but do not yet support the JUnit Platform directly.
Since the JUnit Platform has features that JUnit 4 does not have, the runner is only

#

able to support a subset of the JUnit Platform functionality, especially with regard
to reporting (see Display Names vs. Technical Names). But for the time being the
JUnitPlatform runner is an easy way to get started.

4.4.1. Setup
You need the following artifacts and their dependencies on the classpath. See Dependency Metadata
for details regarding group IDs, artifact IDs, and versions.

68

Explicit Dependencies
¥ junit-platform-runner in test scope: location of the JUnitPlatform runner
¥ junit-4.12.jar in test scope: to run tests using JUnit 4
¥ junit-jupiter-api in test scope: API for writing tests using JUnit Jupiter, including @Test, etc.
¥ junit-jupiter-engine in test runtime scope: implementation of the TestEngine API for JUnit
Jupiter
Transitive Dependencies
¥ junit-platform-suite-api in test scope
¥ junit-platform-launcher in test scope
¥ junit-platform-engine in test scope
¥ junit-platform-commons in test scope
¥ opentest4j in test scope

4.4.2. Display Names vs. Technical Names
To define a custom display name for the class run via @RunWith(JUnitPlatform.class) simply
annotate the class with @SuiteDisplayName and provide a custom value.
By default, display names will be used for test artifacts; however, when the JUnitPlatform runner is
used to execute tests with a build tool such as Gradle or Maven, the generated test report often
needs to include the technical names of test artifacts Ñ for example, fully qualified class names Ñ
instead of shorter display names like the simple name of a test class or a custom display name
containing special characters. To enable technical names for reporting purposes, simply declare the
@UseTechnicalNames annotation alongside @RunWith(JUnitPlatform.class).
Note that the presence of @UseTechnicalNames overrides any custom display name configured via
@SuiteDisplayName.

4.4.3. Single Test Class
One

way

to

use

the

JUnitPlatform

runner

is

to

annotate

a

test

class

with

@RunWith(JUnitPlatform.class) directly. Please note that the test methods in the following example
are annotated with org.junit.jupiter.api.Test (JUnit Jupiter), not org.junit.Test (JUnit Vintage).
Moreover, in this case the test class must be public; otherwise, some IDEs and build tools might not
recognize it as a JUnit 4 test class.

69

import static org.junit.jupiter.api.Assertions.fail;
import org.junit.jupiter.api.Test;
import org.junit.platform.runner.JUnitPlatform;
import org.junit.runner.RunWith;
@RunWith(JUnitPlatform.class)
public class JUnit4ClassDemo {
Ê
Ê
Ê
Ê

@Test
void succeedingTest() {
/* no-op */
}

Ê
Ê
Ê
Ê

@Test
void failingTest() {
fail("Failing for failing's sake.");
}

}

4.4.4. Test Suite
If you have multiple test classes you can create a test suite as can be seen in the following example.

import
import
import
import

org.junit.platform.runner.JUnitPlatform;
org.junit.platform.suite.api.SelectPackages;
org.junit.platform.suite.api.SuiteDisplayName;
org.junit.runner.RunWith;

@RunWith(JUnitPlatform.class)
@SuiteDisplayName("JUnit 4 Suite Demo")
@SelectPackages("example")
public class JUnit4SuiteDemo {
}
The JUnit4SuiteDemo will discover and run all tests in the example package and its subpackages. By
default, it will only include test classes whose names either begin with Test or end with Test or
Tests.

#

70

Additional Configuration Options

There are more configuration options for discovering and filtering tests than just
@SelectPackages. Please consult the Javadoc for further details.

4.5. Configuration Parameters
In addition to instructing the platform which test classes and test engines to include, which
packages to scan, etc., it is sometimes necessary to provide additional custom configuration
parameters that are specific to a particular test engine or registered extension. For example, the
JUnit Jupiter TestEngine supports configuration parameters for the following use cases.
¥ Changing the Default Test Instance Lifecycle
¥ Enabling Automatic Extension Detection
¥ Deactivating Conditions
Configuration Parameters are text-based key-value pairs that can be supplied to test engines
running on the JUnit Platform via one of the following mechanisms.
1. The

configurationParameter()

and

configurationParameters()

methods

in

the

LauncherDiscoveryRequestBuilder which is used to build a request supplied to the Launcher API.
When running tests via one of the tools provided by the JUnit Platform you can specify
configuration parameters as follows:
" Console Launcher: use the --config command-line option.
" Gradle: use the systemProperty or systemProperties DSL.
" Maven Surefire provider: use the configurationParameters property.
2. JVM system properties.
3. The JUnit Platform configuration file: a file named junit-platform.properties in the root of the
class path that follows the syntax rules for a Java Properties file.
Configuration parameters are looked up in the exact order defined above.

#

Consequently, configuration parameters supplied directly to the Launcher take
precedence over those supplied via system properties and the configuration file.
Similarly,

configuration

parameters

supplied

via

system

properties

take

precedence over those supplied via the configuration file.

4.6. Tag Expressions
Tag expressions are boolean expressions with the operators !, & and |. In addition, ( and ) can be
used to adjust for operator precedence.
Table 1. Operators (in descending order of precedence)

Operator

Meaning

Associativity

!

not

right

&

and

left

|

or

left

If you are tagging your tests across multiple dimensions, tag expressions help you to select which
tests to execute. Tagging by test type (e.g. micro, integration, end-to-end) and feature (e.g. foo, bar,

71

baz) the following tag expressions can be useful.
Tag Expression

Selection

foo

all tests for foo

bar | baz

all tests for bar plus all tests for baz

bar & baz

all tests for the intersection between bar and baz

foo & !end-to-end

all tests for foo, but not the end-to-end tests

(micro | integration) & (foo | baz)

all micro or integration tests for foo or baz

4.7. Capturing Standard Output/Error
Since version 1.3, the JUnit Platform provides opt-in support for capturing output printed to
System.out and System.err. To enable it, simply set the junit.platform.output.capture.stdout and/or
junit.platform.output.capture.stderr configuration parameter to true. In addition, you may
configure the maximum number of buffered bytes to be used per executed test or container using
junit.platform.output.capture.maxBuffer.
If enabled, the JUnit Platform captures the corresponding output and publishes it as a report entry
using the stdout or stderr keys to all registered TestExecutionListener instances immediately before
reporting the test or container as finished.
Please note that the captured output will only contain output emitted by the thread that was used to
execute a container or test. Any output by other threads will be omitted because particularly when
executing tests in parallel it would be impossible to attribute it to a specific test or container.

"

Capturing output is currently an experimental feature. YouÕre invited to give it a try
and provide feedback to the JUnit team so they can improve and eventually
promote this feature.

5. Extension Model
5.1. Overview
In contrast to the competing Runner, @Rule, and @ClassRule extension points in JUnit 4, the JUnit
Jupiter extension model consists of a single, coherent concept: the Extension API. Note, however,
that Extension itself is just a marker interface.

5.2. Registering Extensions
Extensions

can

be

registered

declaratively

via

@ExtendWith,

programmatically

via

@RegisterExtension, or automatically via JavaÕs ServiceLoader mechanism.

5.2.1. Declarative Extension Registration
Developers can register one or more extensions declaratively by annotating a test interface, test

72

class, test method, or custom composed annotation with @ExtendWith(É) and supplying class
references for the extensions to register.
For example, to register a custom RandomParametersExtension for a particular test method, you
would annotate the test method as follows.

@ExtendWith(RandomParametersExtension.class)
@Test
void test(@Random int i) {
Ê
// ...
}
To register a custom RandomParametersExtension for all tests in a particular class and its subclasses,
you would annotate the test class as follows.

@ExtendWith(RandomParametersExtension.class)
class MyTests {
Ê
// ...
}
Multiple extensions can be registered together like this:

@ExtendWith({ FooExtension.class, BarExtension.class })
class MyFirstTests {
Ê
// ...
}
As an alternative, multiple extensions can be registered separately like this:

@ExtendWith(FooExtension.class)
@ExtendWith(BarExtension.class)
class MySecondTests {
Ê
// ...
}

Extension Registration Order

#

Extensions registered declaratively via @ExtendWith will be executed in the order in
which they are declared in the source code. For example, the execution of tests in
both MyFirstTests and MySecondTests will be extended by the FooExtension and
BarExtension, in exactly that order.

5.2.2. Programmatic Extension Registration
Developers can register extensions programmatically by annotating fields in test classes with
@RegisterExtension.

73

When an extension is registered declaratively via @ExtendWith, it can typically only be configured via
annotations. In contrast, when an extension is registered via @RegisterExtension, it can be
configured programmatically!Ñ!for example, in order to pass arguments to the extensionÕs
constructor, a static factory method, or a builder API.

#

@RegisterExtension fields must not be private or null (at evaluation time) but may
be either static or non-static.

Static Fields
If a @RegisterExtension field is static, the extension will be registered after extensions that are
registered at the class level via @ExtendWith. Such static extensions are not limited in which
extension APIs they can implement. Extensions registered via static fields may therefore implement
class-level and instance-level extension APIs such as BeforeAllCallback, AfterAllCallback, and
TestInstancePostProcessor as well as method-level extension APIs such as BeforeEachCallback, etc.
In the following example, the server field in the test class is initialized programmatically by using a
builder pattern supported by the WebServerExtension. The configured WebServerExtension will be
automatically registered as an extension at the class level!Ñ!for example, in order to start the
server before all tests in the class and then stop the server after all tests in the class have
completed. In addition, static lifecycle methods annotated with @BeforeAll or @AfterAll as well as
@BeforeEach, @AfterEach, and @Test methods can access the instance of the extension via the server
field if necessary.
An extension registered via a static field

class WebServerDemo {
Ê
Ê
Ê
Ê

@RegisterExtension
static WebServerExtension server = WebServerExtension.builder()
.enableSecurity(false)
.build();

Ê
Ê
Ê
Ê
Ê
Ê
Ê

@Test
void getProductList() {
WebClient webClient = new WebClient();
String serverUrl = server.getServerUrl();
// Use WebClient to connect to web server using serverUrl and verify response
assertEquals(200, webClient.get(serverUrl + "/products").getResponseStatus());
}

}

Static Fields in Kotlin
The Kotlin programming language does not have the concept of a static field. However, the
compiler can be instructed to generate static fields using annotations. Since, as stated earlier,
@RegisterExtension fields must not be private nor null, one cannot use the @JvmStatic annotation in
Kotlin as it generates private fields. Rather, the @JvmField annotation must be used.

74

The following example is a version of the WebServerDemo from the previous section that has been
ported to Kotlin.
Registering an extension via a static field in Kotlin

class KotlinWebServerDemo {
Ê
Ê
Ê
Ê
Ê
Ê
Ê

companion object {
@JvmField
@RegisterExtension
val server = WebServerExtension.builder()
.enableSecurity(false)
.build()
}

Ê
Ê
Ê
Ê
Ê
Ê
Ê
}

@Test
fun getProductList() {
// Use WebClient to connect to web server using serverUrl and verify response
val webClient = WebClient()
val serverUrl = server.serverUrl
assertEquals(200, webClient.get("$serverUrl/products").responseStatus)
}

Instance Fields
If a @RegisterExtension field is non-static (i.e., an instance field), the extension will be registered
after the test class has been instantiated and after each registered TestInstancePostProcessor has
been given a chance to post-process the test instance (potentially injecting the instance of the
extension to be used into the annotated field). Thus, if such an instance extension implements classlevel

or

instance-level

extension

APIs

such

as

BeforeAllCallback,

AfterAllCallback,

or

TestInstancePostProcessor, those APIs will not be honored. By default, an instance extension will be
registered after extensions that are registered at the method level via @ExtendWith; however, if the
test class is configured with @TestInstance(Lifecycle.PER_CLASS) semantics, an instance extension
will be registered before extensions that are registered at the method level via @ExtendWith.
In the following example, the docs field in the test class is initialized programmatically by invoking
a custom lookUpDocsDir() method and supplying the result to the static forPath() factory method in
the DocumentationExtension. The configured DocumentationExtension will be automatically registered
as an extension at the method level. In addition, @BeforeEach, @AfterEach, and @Test methods can
access the instance of the extension via the docs field if necessary.

75

An extension registered via an instance field

class DocumentationDemo {
Ê
Ê
Ê

static Path lookUpDocsDir() {
// return path to docs dir
}

Ê
Ê

@RegisterExtension
DocumentationExtension docs = DocumentationExtension.forPath(lookUpDocsDir());

Ê
Ê
Ê
Ê
}

@Test
void generateDocumentation() {
// use this.docs ...
}

5.2.3. Automatic Extension Registration
In addition to declarative extension registration and programmatic extension registration support
using

annotations,

JUnit

Jupiter

also

supports

global

extension

registration

via

JavaÕs

java.util.ServiceLoader mechanism, allowing third-party extensions to be auto-detected and
automatically registered based on what is available in the classpath.
Specifically, a custom extension can be registered by supplying its fully qualified class name in a file
named org.junit.jupiter.api.extension.Extension within the /META-INF/services folder in its
enclosing JAR file.
Enabling Automatic Extension Detection
Auto-detection is an advanced feature and is therefore not enabled by default. To enable it, simply
set the junit.jupiter.extensions.autodetection.enabled configuration parameter to true. This can be
supplied as a JVM system property, as a configuration parameter in the LauncherDiscoveryRequest
that is passed to the Launcher, or via the JUnit Platform configuration file (see Configuration
Parameters for details).
For example, to enable auto-detection of extensions, you can start your JVM with the following
system property.
-Djunit.jupiter.extensions.autodetection.enabled=true
When auto-detection is enabled, extensions discovered via the ServiceLoader mechanism will be
added to the extension registry after JUnit JupiterÕs global extensions (e.g., support for TestInfo,
TestReporter, etc.).

5.2.4. Extension Inheritance
Registered extensions are inherited within test class hierarchies with top-down semantics.
Similarly, extensions registered at the class-level are inherited at the method-level. Furthermore, a
specific extension implementation can only be registered once for a given extension context and its

76

parent contexts. Consequently, any attempt to register a duplicate extension implementation will be
ignored.

5.3. Conditional Test Execution
ExecutionCondition defines the Extension API for programmatic, conditional test execution.
An ExecutionCondition is evaluated for each container (e.g., a test class) to determine if all the tests it
contains

should

be

executed

based

on

the

supplied

ExtensionContext.

Similarly,

an

ExecutionCondition is evaluated for each test to determine if a given test method should be executed
based on the supplied ExtensionContext.
When multiple ExecutionCondition extensions are registered, a container or test is disabled as soon
as one of the conditions returns disabled. Thus, there is no guarantee that a condition is evaluated
because another extension might have already caused a container or test to be disabled. In other
words, the evaluation works like the short-circuiting boolean OR operator.
See the source code of DisabledCondition and @Disabled for concrete examples.

5.3.1. Deactivating Conditions
Sometimes it can be useful to run a test suite without certain conditions being active. For example,
you may wish to run tests even if they are annotated with @Disabled in order to see if they are still
broken. To do this, simply provide a pattern for the junit.jupiter.conditions.deactivate
configuration parameter to specify which conditions should be deactivated (i.e., not evaluated) for
the current test run. The pattern can be supplied as a JVM system property, as a configuration
parameter in the LauncherDiscoveryRequest that is passed to the Launcher, or via the JUnit Platform
configuration file (see Configuration Parameters for details).
For example, to deactivate JUnitÕs @Disabled condition, you can start your JVM with the following
system property.
-Djunit.jupiter.conditions.deactivate=org.junit.*DisabledCondition
Pattern Matching Syntax
If the junit.jupiter.conditions.deactivate pattern consists solely of an asterisk (*), all conditions
will be deactivated. Otherwise, the pattern will be used to match against the fully qualified class
name (FQCN) of each registered condition. Any dot (.) in the pattern will match against a dot (.) or
a dollar sign ($) in the FQCN. Any asterisk (*) will match against one or more characters in the
FQCN. All other characters in the pattern will be matched one-to-one against the FQCN.
Examples:
¥ *: deactivates all conditions.
¥ org.junit.*: deactivates every condition under the org.junit base package and any of its
subpackages.
¥ *.MyCondition: deactivates every condition whose simple class name is exactly MyCondition.
¥ *System*: deactivates every condition whose simple class name contains System.
77

¥ org.example.MyCondition:

deactivates

the

condition

whose

FQCN

is

exactly

org.example.MyCondition.

5.4. Test Instance Factories
TestInstanceFactory defines the API for Extensions that wish to create test class instances.
Common use cases include acquiring the test instance from a dependency injection framework or
invoking a static factory method to create the test class instance.
If no TestInstanceFactory is registered, the framework will simply invoke the sole constructor for
the test class to instantiate it, potentially resolving constructor arguments via registered
ParameterResolver extensions.
Extensions that implement TestInstanceFactory can be registered on test interfaces, top-level test
classes, or @Nested test classes.
Registering multiple extensions that implement TestInstanceFactory for any single
class will result in an exception being thrown for all tests in that class, in any
subclass, and in any nested class. Note that any TestInstanceFactory registered in a

"

superclass or enclosing class (i.e., in the case of a @Nested test class) is inherited. It is
the userÕs responsibility to ensure that only a single TestInstanceFactory is
registered for any specific test class.

5.5. Test Instance Post-processing
TestInstancePostProcessor defines the API for Extensions that wish to post process test instances.
Common use cases include injecting dependencies into the test instance, invoking custom
initialization methods on the test instance, etc.
For a concrete example, consult the source code for the MockitoExtension and the SpringExtension.

5.6. Parameter Resolution
ParameterResolver defines the Extension API for dynamically resolving parameters at runtime.
If a test constructor or a @Test, @RepeatedTest, @ParameterizedTest, @TestFactory, @BeforeEach,
@AfterEach, @BeforeAll, or @AfterAll method accepts a parameter, the parameter must be resolved at
runtime

by

a

ParameterResolver.

A

ParameterResolver

can

either

be

built-in

(see

TestInfoParameterResolver) or registered by the user. Generally speaking, parameters may be
resolved by name, type, annotation, or any combination thereof. For concrete examples, consult the
source code for CustomTypeParameterResolver and CustomAnnotationParameterResolver.

78

Due to a bug in the byte code generated by javac on JDK versions prior to JDK 9,
looking

up

annotations

on

parameters

directly

via

the

core

java.lang.reflect.Parameter API will always fail for inner class constructors (e.g., a
constructor in a @Nested test class).
The ParameterContext API supplied to ParameterResolver implementations therefore

"

includes the following convenience methods for correctly looking up annotations
on parameters. Extension authors are strongly encouraged to use these methods
instead of those provided in java.lang.reflect.Parameter in order to avoid this bug
in the JDK.
¥ boolean isAnnotated(Class annotationType)
¥ Optional findAnnotation(Class annotationType)
¥ List findRepeatableAnnotations(Class annotationType)

5.7. Test Lifecycle Callbacks
The following interfaces define the APIs for extending tests at various points in the test execution
lifecycle. Consult the following sections for examples and the Javadoc for each of these interfaces in
the org.junit.jupiter.api.extension package for further details.
¥ BeforeAllCallback
" BeforeEachCallback
$ BeforeTestExecutionCallback
$ AfterTestExecutionCallback
" AfterEachCallback
¥ AfterAllCallback
Implementing Multiple Extension APIs

#

Extension developers may choose to implement any number of these interfaces
within a single extension. Consult the source code of the SpringExtension for a
concrete example.

5.7.1. Before and After Test Execution Callbacks
BeforeTestExecutionCallback and AfterTestExecutionCallback define the APIs for Extensions that
wish to add behavior that will be executed immediately before and immediately after a test method
is executed, respectively. As such, these callbacks are well suited for timing, tracing, and similar use
cases. If you need to implement callbacks that are invoked around @BeforeEach and @AfterEach
methods, implement BeforeEachCallback and AfterEachCallback instead.
The following example shows how to use these callbacks to calculate and log the execution time of
a

test

method.

TimingExtension

implements

both

BeforeTestExecutionCallback

and

AfterTestExecutionCallback in order to time and log the test execution.

79

An extension that times and logs the execution of test methods

import java.lang.reflect.Method;
import java.util.logging.Logger;
import
import
import
import
import

org.junit.jupiter.api.extension.AfterTestExecutionCallback;
org.junit.jupiter.api.extension.BeforeTestExecutionCallback;
org.junit.jupiter.api.extension.ExtensionContext;
org.junit.jupiter.api.extension.ExtensionContext.Namespace;
org.junit.jupiter.api.extension.ExtensionContext.Store;

public class TimingExtension implements BeforeTestExecutionCallback,
AfterTestExecutionCallback {
Ê
private static final Logger logger = Logger.getLogger(TimingExtension.class
.getName());
Ê

private static final String START_TIME = "start time";

Ê
Ê
Ê
Ê

@Override
public void beforeTestExecution(ExtensionContext context) throws Exception {
getStore(context).put(START_TIME, System.currentTimeMillis());
}

Ê
Ê
Ê
Ê
Ê

@Override
public void afterTestExecution(ExtensionContext context) throws Exception {
Method testMethod = context.getRequiredTestMethod();
long startTime = getStore(context).remove(START_TIME, long.class);
long duration = System.currentTimeMillis() - startTime;

Ê
logger.info(() -> String.format("Method [%s] took %s ms.", testMethod.getName
(), duration));
Ê
}
Ê
private Store getStore(ExtensionContext context) {
Ê
return context.getStore(Namespace.create(getClass(), context
.getRequiredTestMethod()));
Ê
}
}
Since the TimingExtensionTests class registers the TimingExtension via @ExtendWith, its tests will have
this timing applied when they execute.

80

A test class that uses the example TimingExtension

@ExtendWith(TimingExtension.class)
class TimingExtensionTests {
Ê
Ê
Ê
Ê

@Test
void sleep20ms() throws Exception {
Thread.sleep(20);
}

Ê
Ê
Ê
Ê

@Test
void sleep50ms() throws Exception {
Thread.sleep(50);
}

}
The following is an example of the logging produced when TimingExtensionTests is run.

INFO: Method [sleep20ms] took 24 ms.
INFO: Method [sleep50ms] took 53 ms.

5.8. Exception Handling
TestExecutionExceptionHandler defines the API for Extensions that wish to handle exceptions thrown
during test execution.
The following example shows an extension which will swallow all instances of IOException but
rethrow any other type of exception.
An exception handling extension

public class IgnoreIOExceptionExtension implements TestExecutionExceptionHandler {
Ê
@Override
Ê
public void handleTestExecutionException(ExtensionContext context, Throwable
throwable)
Ê
throws Throwable {
Ê
Ê
Ê
Ê
Ê
}

if (throwable instanceof IOException) {
return;
}
throw throwable;
}

81

5.9. Providing Invocation Contexts for Test Templates
A

@TestTemplate

method

can

only

be

executed

when

at

least

one

TestTemplateInvocationContextProvider is registered. Each such provider is responsible for
providing a Stream of TestTemplateInvocationContext instances. Each context may specify a custom
display name and a list of additional extensions that will only be used for the next invocation of the
@TestTemplate method.
The following example shows how to write a test template as well as how to register and implement
a TestTemplateInvocationContextProvider.

82

A test template with accompanying extension

@TestTemplate
@ExtendWith(MyTestTemplateInvocationContextProvider.class)
void testTemplate(String parameter) {
Ê
assertEquals(3, parameter.length());
}
public class MyTestTemplateInvocationContextProvider implements
TestTemplateInvocationContextProvider {
Ê
@Override
Ê
public boolean supportsTestTemplate(ExtensionContext context) {
Ê
return true;
Ê
}
Ê
@Override
Ê
public Stream
provideTestTemplateInvocationContexts(ExtensionContext context) {
Ê
return Stream.of(invocationContext("foo"), invocationContext("bar"));
Ê
}
Ê
Ê
Ê
Ê
Ê
Ê

private TestTemplateInvocationContext invocationContext(String parameter) {
return new TestTemplateInvocationContext() {
@Override
public String getDisplayName(int invocationIndex) {
return parameter;
}

Ê
@Override
Ê
public List getAdditionalExtensions() {
Ê
return Collections.singletonList(new ParameterResolver() {
Ê
@Override
Ê
public boolean supportsParameter(ParameterContext
parameterContext,
Ê
ExtensionContext extensionContext) {
Ê
return parameterContext.getParameter().getType().equals(
String.class);
Ê
}
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
Ê
}

@Override
public Object resolveParameter(ParameterContext parameterContext,
ExtensionContext extensionContext) {
return parameter;
}
});
}
};
}

83

In this example, the test template will be invoked twice. The display names of the invocations will
be ÒfooÓ and ÒbarÓ as specified by the invocation context. Each invocation registers a custom
ParameterResolver which is used to resolve the method parameter. The output when using the
ConsoleLauncher is as follows.

'$ testTemplate(String) %
Ê #$ foo %
Ê '$ bar %
The TestTemplateInvocationContextProvider extension API is primarily intended for implementing
different kinds of tests that rely on repetitive invocation of a test-like method albeit in different
contexts Ñ for example, with different parameters, by preparing the test class instance differently,
or multiple times without modifying the context. Please refer to the implementations of Repeated
Tests or Parameterized Tests which use this extension point to provide their functionality.

5.10. Keeping State in Extensions
Usually, an extension is instantiated only once. So the question becomes relevant: How do you keep
the state from one invocation of an extension to the next? The ExtensionContext API provides a
Store exactly for this purpose. Extensions may put values into a store for later retrieval. See the
TimingExtension for an example of using the Store with a method-level scope. It is important to
remember that values stored in an ExtensionContext during test execution will not be available in
the surrounding ExtensionContext. Since ExtensionContexts may be nested, the scope of inner
contexts may also be limited. Consult the corresponding JavaDoc for details on the methods
available for storing and retrieving values via the Store.
ExtensionContext.Store.CloseableResource

#

An extension context store is bound to its extension context lifecycle. When an
extension context lifecycle ends it closes its associated store. All stored values that
are instances of CloseableResource are notified by an invocation of their close()
method.

5.11. Supported Utilities in Extensions
The junit-platform-commons artifact exposes a package named org.junit.platform.commons.support
that contains maintained utility methods for working with annotations, classes, reflection, and
classpath scanning tasks. TestEngine and Extension authors are encouraged to use these supported
methods in order to align with the behavior of the JUnit Platform.

5.11.1. Annotation Support
AnnotationSupport provides static utility methods that operate on annotated elements (e.g.,
packages, annotations, classes, interfaces, constructors, methods, and fields). These include
methods to check whether an element is annotated or meta-annotated with a particular annotation,
to search for specific annotations, and to find annotated methods and fields in a class or interface.
Some of these methods search on implemented interfaces and within class hierarchies to find

84

annotations. Consult the JavaDoc for AnnotationSupport for further details.

5.11.2. Class Support
ClassSupport provides static utility methods for working with classes (i.e., instances of
java.lang.Class). Consult the JavaDoc for ClassSupport for further details.

5.11.3. Reflection Support
ReflectionSupport provides static utility methods that augment the standard JDK reflection and
class-loading mechanisms. These include methods to scan the classpath in search of classes
matching specified predicates, to load and create new instances of a class, and to find and invoke
methods. Some of these methods traverse class hierarchies to locate matching methods. Consult the
JavaDoc for ReflectionSupport for further details.

5.12. Relative Execution Order of User Code and
Extensions
When executing a test class that contains one or more test methods, a number of extension
callbacks are called in addition to the user-provided test and lifecycle methods. The following
diagram illustrates the relative order of user-provided code and extension code.

User code and extension code

User-provided test and lifecycle methods are shown in orange, with callback code provided by
extensions shown in blue. The grey box denotes the execution of a single test method and will be
repeated for every test method in the test class.
The following table further explains the twelve steps in the User code and extension code diagram.

85

Ste Interface/An Description
p
notation
1

interface
extension code executed before all tests of the container are executed
org.junit.jup
iter.api.exte
nsion.BeforeA
llCallback

2

annotation
user code executed before all tests of the container are executed
org.junit.jup
iter.api.Befo
reAll

3

interface
extension code executed before each test is executed
org.junit.jup
iter.api.exte
nsion.BeforeE
achCallback

4

annotation
user code executed before each test is executed
org.junit.jup
iter.api.Befo
reEach

5

interface
extension code executed immediately before a test is executed
org.junit.jup
iter.api.exte
nsion.BeforeT
estExecutionC
allback

6

annotation
user code of the actual test method
org.junit.jup
iter.api.Test

7

interface
extension code for handling exceptions thrown during a test
org.junit.jup
iter.api.exte
nsion.TestExe
cutionExcepti
onHandler

8

interface
extension code executed immediately after test execution and its
org.junit.jup corresponding exception handlers
iter.api.exte
nsion.AfterTe
stExecutionCa
llback

9

annotation
user code executed after each test is executed
org.junit.jup
iter.api.Afte
rEach

10

interface
extension code executed after each test is executed
org.junit.jup
iter.api.exte
nsion.AfterEa
chCallback

11

annotation
user code executed after all tests of the container are executed
org.junit.jup
iter.api.Afte
rAll

86

Ste Interface/An Description
p
notation
12

interface
extension code executed after all tests of the container are executed
org.junit.jup
iter.api.exte
nsion.AfterAl
lCallback

In the simplest case only the actual test method will be executed (step 6); all other steps are optional
depending on the presence of user code or extension support for the corresponding lifecycle
callback. For further details on the various lifecycle callbacks please consult the respective JavaDoc
for each annotation and extension.

6. Migrating from JUnit 4
Although the JUnit Jupiter programming model and extension model will not support JUnit 4
features such as Rules and Runners natively, it is not expected that source code maintainers will
need to update all of their existing tests, test extensions, and custom build test infrastructure to
migrate to JUnit Jupiter.
Instead, JUnit provides a gentle migration path via a JUnit Vintage test engine which allows existing
tests based on JUnit 3 and JUnit 4 to be executed using the JUnit Platform infrastructure. Since all
classes and annotations specific to JUnit Jupiter reside under a new org.junit.jupiter base
package, having both JUnit 4 and JUnit Jupiter in the classpath does not lead to any conflicts. It is
therefore safe to maintain existing JUnit 4 tests alongside JUnit Jupiter tests. Furthermore, since the
JUnit team will continue to provide maintenance and bug fix releases for the JUnit 4.x baseline,
developers have plenty of time to migrate to JUnit Jupiter on their own schedule.

6.1. Running JUnit 4 Tests on the JUnit Platform
Just make sure that the junit-vintage-engine artifact is in your test runtime path. In that case JUnit
3 and JUnit 4 tests will automatically be picked up by the JUnit Platform launcher.
See the example projects in the junit5-samples repository to find out how this is done with Gradle
and Maven.

6.1.1. Categories Support
For test classes or methods that are annotated with @Category, the JUnit Vintage test engine exposes
the categoryÕs fully qualified class name as a tag of the corresponding test identifier. For example, if
a test method is annotated with @Category(Example.class), it will be tagged with "com.acme.Example".
Similar to the Categories runner in JUnit 4, this information can be used to filter the discovered
tests before executing them (see Running Tests for details).

6.2. Migration Tips
The following are things you have to watch out for when migrating existing JUnit 4 tests to JUnit
Jupiter.

87

¥ Annotations reside in the org.junit.jupiter.api package.
¥ Assertions reside in org.junit.jupiter.api.Assertions.
¥ Assumptions reside in org.junit.jupiter.api.Assumptions.
¥ @Before and @After no longer exist; use @BeforeEach and @AfterEach instead.
¥ @BeforeClass and @AfterClass no longer exist; use @BeforeAll and @AfterAll instead.
¥ @Ignore no longer exists: use @Disabled instead.
¥ @Category no longer exists; use @Tag instead.
¥ @RunWith no longer exists; superseded by @ExtendWith.
¥ @Rule and @ClassRule no longer exist; superseded by @ExtendWith; see the following section for
partial rule support.

6.3. Limited JUnit 4 Rule Support
As stated above, JUnit Jupiter does not and will not support JUnit 4 rules natively. The JUnit team
realizes, however, that many organizations, especially large ones, are likely to have large JUnit 4
code bases that make use of custom rules. To serve these organizations and enable a gradual
migration path the JUnit team has decided to support a selection of JUnit 4 rules verbatim within
JUnit Jupiter. This support is based on adapters and is limited to those rules that are semantically
compatible to the JUnit Jupiter extension model, i.e. those that do not completely change the overall
execution flow of the test.
The junit-jupiter-migrationsupport module from JUnit Jupiter currently supports the following
three Rule types including subclasses of those types:
¥ org.junit.rules.ExternalResource (including org.junit.rules.TemporaryFolder)
¥ org.junit.rules.Verifier (including org.junit.rules.ErrorCollector)
¥ org.junit.rules.ExpectedException
As in JUnit 4, Rule-annotated fields as well as methods are supported. By using these class-level
extensions on a test class such Rule implementations in legacy code bases can be left unchanged
including the JUnit 4 rule import statements.
This limited form of Rule support can be switched on by the class-level annotation
org.junit.jupiter.migrationsupport.rules.EnableRuleMigrationSupport.
composed

annotation

which

enables

all

migration

support

This

annotation

extensions:

is

a

VerifierSupport,

ExternalResourceSupport, and ExpectedExceptionSupport.
However, if you intend to develop a new extension for JUnit 5 please use the new extension model
of JUnit Jupiter instead of the rule-based model of JUnit 4.

"

88

JUnit 4 Rule support in JUnit Jupiter is currently an experimental feature. Consult
the table in Experimental APIs for detail.

7. Advanced Topics
7.1. JUnit Platform Launcher API
One of the prominent goals of JUnit 5 is to make the interface between JUnit and its programmatic
clients Ð build tools and IDEs Ð more powerful and stable. The purpose is to decouple the internals
of discovering and executing tests from all the filtering and configuration thatÕs necessary from the
outside.
JUnit 5 introduces the concept of a Launcher that can be used to discover, filter, and execute tests.
Moreover, third party test libraries Ð like Spock, Cucumber, and FitNesse Ð can plug into the JUnit
PlatformÕs launching infrastructure by providing a custom TestEngine.
The launcher API is in the junit-platform-launcher module.
An example consumer of the launcher API is the ConsoleLauncher in the junit-platform-console
project.

7.1.1. Discovering Tests
Introducing test discovery as a dedicated feature of the platform itself will (hopefully) free IDEs and
build tools from most of the difficulties they had to go through to identify test classes and test
methods in the past.
Usage Example:

import static
org.junit.platform.engine.discovery.ClassNameFilter.includeClassNamePatterns;
import static org.junit.platform.engine.discovery.DiscoverySelectors.selectClass;
import static org.junit.platform.engine.discovery.DiscoverySelectors.selectPackage;
import
import
import
import
import
import
import
import

org.junit.platform.launcher.Launcher;
org.junit.platform.launcher.LauncherDiscoveryRequest;
org.junit.platform.launcher.TestExecutionListener;
org.junit.platform.launcher.TestPlan;
org.junit.platform.launcher.core.LauncherConfig;
org.junit.platform.launcher.core.LauncherDiscoveryRequestBuilder;
org.junit.platform.launcher.core.LauncherFactory;
org.junit.platform.launcher.listeners.SummaryGeneratingListener;

89

LauncherDiscoveryRequest request = LauncherDiscoveryRequestBuilder.request()
Ê
.selectors(
Ê
selectPackage("com.example.mytests"),
Ê
selectClass(MyTestClass.class)
Ê
)
Ê
.filters(
Ê
includeClassNamePatterns(".*Tests")
Ê
)
Ê
.build();
Launcher launcher = LauncherFactory.create();
TestPlan testPlan = launcher.discover(request);
ThereÕs currently the possibility to select classes, methods, and all classes in a package or even
search for all tests in the classpath. Discovery takes place across all participating test engines.
The resulting TestPlan is a hierarchical (and read-only) description of all engines, classes, and test
methods that fit the LauncherDiscoveryRequest. The client can traverse the tree, retrieve details
about a node, and get a link to the original source (like class, method, or file position). Every node in
the test plan has a unique ID that can be used to invoke a particular test or group of tests.

7.1.2. Executing Tests
To execute tests, clients can use the same LauncherDiscoveryRequest as in the discovery phase or
create a new request. Test progress and reporting can be achieved by registering one or more
TestExecutionListener implementations with the Launcher as in the following example.

LauncherDiscoveryRequest request = LauncherDiscoveryRequestBuilder.request()
Ê
.selectors(
Ê
selectPackage("com.example.mytests"),
Ê
selectClass(MyTestClass.class)
Ê
)
Ê
.filters(
Ê
includeClassNamePatterns(".*Tests")
Ê
)
Ê
.build();
Launcher launcher = LauncherFactory.create();
// Register a listener of your choice
TestExecutionListener listener = new SummaryGeneratingListener();
launcher.registerTestExecutionListeners(listener);
launcher.execute(request);
There is no return value for the execute() method, but you can easily use a listener to aggregate the
final results in an object of your own. For an example see the SummaryGeneratingListener.

90

7.1.3. Plugging in your own Test Engine
JUnit currently provides two TestEngine implementations.
¥ junit-jupiter-engine: The core of JUnit Jupiter.
¥ junit-vintage-engine: A thin layer on top of JUnit 4 to allow running vintage tests with the
launcher infrastructure.
Third parties may also contribute their own TestEngine by implementing the interfaces in the junitplatform-engine module and registering their engine. By default, engine registration is supported
via JavaÕs java.util.ServiceLoader mechanism. For example, the junit-jupiter-engine module
registers

its

org.junit.jupiter.engine.JupiterTestEngine

in

a

file

named

org.junit.platform.engine.TestEngine within the /META-INF/services in the junit-jupiter-engine
JAR.
HierarchicalTestEngine is a convenient abstract base implementation (used by the

#

junit-jupiter-engine) that only requires implementors to provide the logic for test
discovery. It implements execution of TestDescriptors that implement the Node
interface, including support for parallel execution.
The junit- prefix is reserved for TestEngines from the JUnit Team

The JUnit Platform Launcher enforces that only TestEngine implementations
published by the JUnit Team may use the junit- prefix for their TestEngine IDs.

"

¥ If any third-party TestEngine claims to be junit-jupiter or junit-vintage, an
exception will be thrown, immediately halting execution of the JUnit Platform.
¥ If any third-party TestEngine uses the junit- prefix for its ID, a warning
message will be logged. Later releases of the JUnit Platform will throw an
exception for such violations.

7.1.4. Plugging in your own Test Execution Listener
In addition to the public Launcher API method for registering test execution listeners
programmatically, by default custom TestExecutionListener implementations will be discovered at
runtime via JavaÕs java.util.ServiceLoader mechanism and automatically registered with the
Launcher created via the LauncherFactory. For example, an example.TestInfoPrinter class
implementing

TestExecutionListener

and

declared

within

the

/META-

INF/services/org.junit.platform.launcher.TestExecutionListener file is loaded and registered
automatically.

7.1.5. Configuring the Launcher
If you require fine-grained control over automatic detection and registration of test engines and
test execution listeners, you may create an instance of LauncherConfig and supply that to the
LauncherFactory.create(LauncherConfig) method. Typically an instance of LauncherConfig is created
via the built-in fluent builder API, as demonstrated in the following example.

91

LauncherConfig launcherConfig = LauncherConfig.builder()
Ê
.enableTestEngineAutoRegistration(false)
Ê
.enableTestExecutionListenerAutoRegistration(false)
Ê
.addTestEngines(new CustomTestEngine())
Ê
.addTestExecutionListeners(new CustomTestExecutionListener())
Ê
.build();
Launcher launcher = LauncherFactory.create(launcherConfig);
LauncherDiscoveryRequest request = LauncherDiscoveryRequestBuilder.request()
Ê
.selectors(selectPackage("com.example.mytests"))
Ê
.build();
launcher.execute(request);

8. API Evolution
One of the major goals of JUnit 5 is to improve maintainers' capabilities to evolve JUnit despite its
being used in many projects. With JUnit 4 a lot of stuff that was originally added as an internal
construct only got used by external extension writers and tool builders. That made changing JUnit 4
especially difficult and sometimes impossible.
ThatÕs why JUnit 5 introduces a defined lifecycle for all publicly available interfaces, classes, and
methods.

8.1. API Version and Status
Every published artifact has a version number .., and all publicly available
interfaces, classes, and methods are annotated with @API from the @API Guardian project. The
annotationÕs status attribute can be assigned one of the following values.
Status

Description

INTERNAL

Must not be used by any code other than JUnit itself. Might be removed
without prior notice.

DEPRECATED

Should no longer be used; might disappear in the next minor release.

EXPERIMENTAL

Intended for new, experimental features where we are looking for feedback.
Use this element with caution; it might be promoted to MAINTAINED or STABLE in
the future, but might also be removed without prior notice, even in a patch.

MAINTAINED

Intended for features that will not be changed in a backwards- incompatible
way for at least the next minor release of the current major version. If
scheduled for removal, it will be demoted to DEPRECATED first.

STABLE

Intended for features that will not be changed in a backwards- incompatible
way in the current major version (5.*).

If the @API annotation is present on a type, it is considered to be applicable for all public members
of that type as well. A member is allowed to declare a different status value of lower stability.

92

8.2. Experimental APIs
The following table lists which APIs are currently designated as experimental via @API(status =
EXPERIMENTAL). Caution should be taken when relying on such APIs.
Package Name

Type Name

Since

org.junit.jupiter.api

AssertionsKt (class)

5.1

org.junit.jupiter.api.conditio DisabledIf (annotation)
n

5.1

org.junit.jupiter.api.conditio EnabledIf (annotation)
n

5.1

org.junit.jupiter.api.extensio ScriptEvaluationException
n
(class)

5.1

org.junit.jupiter.api.extensio TestInstanceFactory (interface)
n

5.3

org.junit.jupiter.api.extensio TestInstanceFactoryContext
n
(interface)

5.3

org.junit.jupiter.api.extensio TestInstantiationException
n
(class)

5.3

org.junit.jupiter.api.parallel Execution (annotation)

5.3

org.junit.jupiter.api.parallel ExecutionMode (enum)

5.3

org.junit.jupiter.api.parallel ResourceAccessMode (enum)

5.3

org.junit.jupiter.api.parallel ResourceLock (annotation)

5.3

org.junit.jupiter.api.parallel ResourceLocks (annotation)

5.3

org.junit.jupiter.api.parallel Resources (class)

5.3

org.junit.jupiter.params

ParameterizedTest (annotation)

5.0

org.junit.jupiter.params.aggre AggregateWith (annotation)
gator

5.2

org.junit.jupiter.params.aggre ArgumentAccessException (class)
gator

5.2

org.junit.jupiter.params.aggre ArgumentsAccessor (interface)
gator

5.2

org.junit.jupiter.params.aggre ArgumentsAggregationException
gator
(class)

5.2

org.junit.jupiter.params.aggre ArgumentsAggregator (interface)
gator

5.2

org.junit.jupiter.params.conve ArgumentConversionException
rter
(class)

5.0

org.junit.jupiter.params.conve ArgumentConverter (interface)
rter

5.0

org.junit.jupiter.params.conve ConvertWith (annotation)
rter

5.0

org.junit.jupiter.params.conve JavaTimeConversionPattern
rter
(annotation)

5.0

org.junit.jupiter.params.conve SimpleArgumentConverter (class)
rter

5.0

93

Package Name

Type Name

Since

org.junit.jupiter.params.provi Arguments (interface)
der

5.0

org.junit.jupiter.params.provi ArgumentsProvider (interface)
der

5.0

org.junit.jupiter.params.provi ArgumentsSource (annotation)
der

5.0

org.junit.jupiter.params.provi ArgumentsSources (annotation)
der

5.0

org.junit.jupiter.params.provi CsvFileSource (annotation)
der

5.0

org.junit.jupiter.params.provi CsvParsingException (class)
der

5.3

org.junit.jupiter.params.provi CsvSource (annotation)
der

5.0

org.junit.jupiter.params.provi EnumSource (annotation)
der

5.0

org.junit.jupiter.params.provi MethodSource (annotation)
der

5.0

org.junit.jupiter.params.provi ValueSource (annotation)
der

5.0

org.junit.jupiter.params.suppo AnnotationConsumer (interface)
rt

5.0

org.junit.platform.engine.supp PrefixedConfigurationParameter 1.3
ort.config
s (class)
org.junit.platform.engine.supp DefaultParallelExecutionConfig 1.3
ort.hierarchical
urationStrategy (enum)
org.junit.platform.engine.supp ExclusiveResource (class)
ort.hierarchical

1.3

org.junit.platform.engine.supp ForkJoinPoolHierarchicalTestEx 1.3
ort.hierarchical
ecutorService (class)
org.junit.platform.engine.supp HierarchicalTestExecutorServic 1.3
ort.hierarchical
e (interface)
org.junit.platform.engine.supp ExecutionMode (enum)
ort.hierarchical

1.3

org.junit.platform.engine.supp ParallelExecutionConfiguration 1.3
ort.hierarchical
(interface)
org.junit.platform.engine.supp ParallelExecutionConfiguration 1.3
ort.hierarchical
Strategy (interface)
org.junit.platform.engine.supp ResourceLock (interface)
ort.hierarchical

1.3

org.junit.platform.engine.supp SameThreadHierarchicalTestExec 1.3
ort.hierarchical
utorService (class)
org.junit.platform.launcher

LauncherConstants (class)

org.junit.platform.launcher.co LauncherConfig (interface)
re

94

1.3
1.3

8.3. Deprecated APIs
The following table lists which APIs are currently designated as deprecated via @API(status =
DEPRECATED). You should avoid using deprecated APIs whenever possible, since such APIs will likely
be removed in an upcoming release.
Package Name

Type Name

Since

org.junit.platform.engine.supp SingleTestExecutor (class)
ort.hierarchical

1.2

org.junit.platform.surefire.pr JUnitPlatformProvider (class)
ovider

1.3

8.4. @API Tooling Support
The @API Guardian project plans to provide tooling support for publishers and consumers of APIs
annotated with @API. For example, the tooling support will likely provide a means to check if JUnit
APIs are being used in accordance with @API annotation declarations.

9. Contributors
Browse the current list of contributors directly on GitHub.

10. Release Notes
The release notes are available here.

95


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