How to automatically migrate from JUnit 4 to JUnit 5?

Question

In the spirit of this question from JUnit 3 to JUnit 4, are there any list of regular expressions to efficiently migrate from the junit 4 API to the junit 5 API

Answer 1

The tooling at the moment is not great, but improving:

• IntelliJ: Migrates most annotations to JUnit 5 versions. Hovewer, does not do anything if your test file contains @Rules (e.g., ExpectedException) as of v2018.2.
• Error Prone: contains built-in refactorings to automatically migrate various JUnit 4 exception-testing idioms (try/fail/catch/assert, ExpectedExceptions, @Test(expected = …)) to assertThrows, perfectly augmenting IntelliJ.

I recommend the following steps:

1. Add JUnit 5 artefacts to your test dependencies.
2. Install Error Prone compiler.
3. Configure it to produce a patch to migrate to assertThrows, enabling the following checks (the example Maven configuration is below):
   • TryFailRefactoring,
   • ExpectedExceptionRefactoring,
   • TestExceptionRefactoring.
4. Use IntelliJ built-in refactorings to migrate JUnit 4 annotations and methods to JUnit 5 counterparts.

I am not aware of any tools that help to automatically migrate Parameterized tests, or rules other than ExpectedException.

Here is an example Error Prone configuration:

  
    
      maven-compiler-plugin
      3.8.0
      
        javac-with-errorprone
        true
        true
        ${java.compiler.source}
        ${java.compiler.target}
                
          -XepPatchChecks:TryFailRefactoring,ExpectedExceptionRefactoring,TestExceptionRefactoring
          -XepPatchLocation:${project.basedir}
        
      
      
        
          org.codehaus.plexus
          plexus-compiler-javac-errorprone
          2.8.3
        
        
          com.google.errorprone
          error_prone_core
          2.3.2