How do you mock a Sealed class?

Question

Mocking sealed classes can be quite a pain. I currently favor an Adapter pattern to handle this, but something about just keeps feels weird.

So, What is the best way you mock sealed classes?

Java answers are more than welcome. In fact, I would anticipate that the Java community has been dealing with this longer and has a great deal to offer.

But here are some of the .NET opinions:

• Why Duck Typing Matters for C# Develoepers
• Creating wrappers for sealed and other types for mocking
• Unit tests for WCF (and Moq)

Answer 1

My general rule of thumb is that objects that I need to mock should have a common interface too. I think this is right design-wise and makes tests a lot easier (and is usually what you get if you do TDD). More about this can be read in the Google Testing Blog latest post (See point 9).

Also, I've been working mainly in Java in the past 4 years and I can say that I can count on one hand the number of times I've created a final (sealed) class. Another rule here is I should always have a good reason to seal a class, as opposed to sealing it by default.