I'm using JetGroovy to develop Groovy/Grails and quite often I'm seeing that when a unit test is run the stub is executed giving the impression the test passed. Or even worse sometimes a stub is used for the class that is being tested resulting in assertion failures that aren't representative of the real results of the test The only way to get round these problems is to open the file which has a stub and resave it, then re-compile. Sometimes this even doesn't work and I have to fall back to running tests from the command line