Add JUnit 5 to Maven Project | Java Fresher

There are really two pieces to getting JUnit 5 running in Maven: the dependency and the plugin. For the dependency, the easiest thing is the junit-jupiter aggregator artifact, because it pulls in everything I need — the API so my tests compile, the engine so they actually run, and the params module for parameterized tests. I put it in test scope so it never ends up in the production jar.

The second piece is the Maven Surefire plugin, which is what runs unit tests during mvn test. It must support the JUnit Platform; native support starts at 2.22.0, while current projects normally use a 3.x release, and if you forget that, mvn test happily reports zero tests run, which is confusing.

Now, in practice, if I'm on a Spring Boot project I almost never do any of that, because spring-boot-starter-test already bundles JUnit 5, Mockito, AssertJ, and Hamcrest, all in test scope, with compatible versions managed for me. So I just add that one starter and I'm done.

Common mistakes are adding only the junit-jupiter-api artifact, which makes tests compile but not run because the engine is missing, using an old Surefire that silently ignores the tests, and forgetting the test scope.