try{
closure.call() // call the code that tests methodRef in isolation
}
finally{
GroovySystem.metaClassRegistry.removeMetaClass(clazz) // clean up after ourselves
}

I’ve only ever used the interface mocking abilities of EasyMock and haven’t tried it with the class extensions. From a brief look, it appears that using the class extensions to create a partial mock is pretty similar to what I’m doing above. It’s pulling a reference to the method under test and mocking out the rest of the class.

The Test-Specific Subclass pattern is another good alternative. Though it sounds like it might be a bit of work to create a new subclass and maintain the additional instrumentation on the subclass that exposes and controls the state for testing.

I could definitely see that pattern being useful when working with legacy code that you don’t have much control over.

1. Write a test specific subclass and override the method you want to mock out. http://xunitpatterns.com/Test-Specific%20Subclass.html

2. Use the EasyMock class extensions and create a partial mock. http://easymock.org/EasyMock2_3_ClassExtension_Documentation.html

The calling semantics of your test helper is pretty nice though!