Here's an example of a simple test, in which the return type of a Private Static Method within a Class is needed to return a String different from what it would normally return:
And here is the Class itself:
The result of the test execution is always '7:15 AM' and so the test will always fail. This would be a great help in Unit Testing techniques, especially Test Driven Development in Groovy.
It would be great to see Groovy have this capability.