- JUnit 4
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- About
- Last Published: 2025-06-24
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- Version: 4.13.2
JUnit is a simple framework to write repeatable tests. It is an instance of the xUnit architecture for unit testing frameworks.
JUnit 4 is in maintenance mode.
At this point, only critical bugs and security issues will be fixed.
All other issues and PRs will therefore be declined.
For ongoing development, please check out thejunit-framework repository.
@Test public void newArrayListsHaveNoElements() { assertThat(new ArrayList<Integer>().size(), is(0)); } @Test public void sizeReturnsNumberOfElements() { List<Object> instance = new ArrayList<Object>(); instance.add(new Object()); instance.add(new Object()); assertThat(instance.size(), is(2)); }Annotations
Start by marking your tests with@Test.
@Test public void lookupEmailAddresses() { assertThat(new CartoonCharacterEmailLookupService().getResults("looney"), allOf( not(empty()), containsInAnyOrder( allOf(instanceOf(Map.class), hasEntry("id", "56"), hasEntry("email", "[email protected]")), allOf(instanceOf(Map.class), hasEntry("id", "76"), hasEntry("email", "[email protected]")) ) )); }Hamcrest matchers
Make your assertions more expressive and get better failure reports in return.
Welcome
Usage and Idioms
- Assertions
- Test Runners
- Aggregating tests in Suites
- Test Execution Order
- Exception Testing
- Matchers and assertThat
- Ignoring Tests
- Timeout for Tests
- Parameterized Tests
- Assumptions with Assume
- Rules
- Theories
- Test Fixtures
- Categories
- Use with Maven
- Multithreaded code and Concurrency
- Java contract test helpers
- Continuous Testing
Third-party extensions
- Custom Runners
- net.trajano.commons:commons-testing for UtilityClassTestUtil per #646
- System Rules – A collection of JUnit rules for testing code that uses java.lang.System.
- JUnit Toolbox - Provides runners for parallel testing, aPoolingWait class to ease asynchronous testing, and aWildcardPatternSuite which allow you to specify wildcard patterns instead of explicitly listing all classes when you create a suite class.
- junit-quickcheck - QuickCheck-style parameter suppliers for JUnit theories. Usesjunit.contrib's version of the theories machinery, which respects generics on theory parameters.