[mamon]

>> Java has all methods virtual and testing could be done without requiring the interface.

Not sure what you mean by that. I thought that interface/implementation divide is the way to implement virtual calls. Unless you want testing frameworks to do bytecode instrumentation.

[avmich]

If your interface is going to be implemented by just one class, I'd offer to skip interface - it reduces amount of code. If you still need to pass, as a parameter, a class A in order to test a class B, you can instead pass class C inherited from A, with all necessary methods overloaded.

If you just create a class A in java, no interfaces involved, class A will have its methods virtual. I'm not sure what do you mean by interface/implementation divide.

[nitrogen]

Modern testing frameworks can indeed mock concrete classes, which beats the bytecode generation that Spring would be doing anyway.