To combine JUnit 4 and JUnit 5 tests in the same module we need to include JUnit Vintage which provides a TestEngine for running JUnit 4 tests otherwise none of the JUnit 4 tests will be executed. The only effected module so far is the ArjunaCore arjuna module (org.jboss.narayana.arjunacore:arjuna) since that's the only one containing JUnit 5 tests.