Mocks and Stubs

Question

I really don't understand what Mocks and Stubs are. I want to know when, why and how we use Mocks in our test cases. I know that there are good frameworks out there for Mocks and Stubs in Ruby on Rails, but without knowing the purpose, I'm reluctant to use them in my app.

Can you please clarify about Mocks and Stubs? Please help.

Answer 1

My very simplified answer is:

• mocks are objects that have a similar interface as something else
• stubs are fake methods and return a specific answer

With both we are trying to achieve the same thing: we want to test a specific unit (model/view/controller/module) in isolation. E.g. when we are testing the controller, we do not want to test our model, so we use a mock. We want to make sure the correct methods are called, e.g. find. So on our mock, we have a stub that will return something predefined, without actually going to the database.

So we test for expectations: the methods that we expect to be called (on other units), without actually calling them. The test of that specific method, should have been covered in its own test.