What Are the Advantages of Mocha Over Rspec's Built in Mocking Framework

What are the advantages of Mocha over RSpec's built in mocking framework?

One specific feature I really like is being able to stub out all instances of a class. A lot of times I do something like the following with RSpec mocks:

stub_car = mock(Car)
stub_car.stub!(:speed).and_return(100)
Car.stub!(:new).and_return(stub_car)

with Mocha that becomes:

Car.any_instance.stubs(:speed).returns(100)

I find the Mocha version clearer and more explicit.

Is there a way to undo Mocha stubbing of any_instance?

You need to manually configure RSpec.

Rspec.configure do |config|
  ...

  # == Mock Framework
  #
  # If you prefer to use mocha, flexmock or RR, uncomment the appropriate line:
  #
  config.mock_with :mocha
  # config.mock_with :flexmock
  # config.mock_with :rr
  # config.mock_with :rspec
end

Also, remember that Rspec provides its own methods to mock an object. Use the RSpec API or you won't be able to benefit from library abstraction.
http://rspec.info/documentation/mocks/message_expectations.html

How to mock an instance method of an already mocked object?

You could try something like this :-

user = Factory(:user)
user.stubs(:facebook => stub(:me => stub(:info => {:name => "John Doe"})))

If you really want to check that all these methods are called (which I suspect you don't), you could do the following :-

user = Factory(:user)
user.expects(:facebook => mock(:me => mock(:info => {:name => "John Doe"})))

It's a bit more verbose, but it's usually worthwhile giving each mock object a name :-

user = Factory(:user)
user.stubs(:facebook => stub('facebook', :me => stub('me', :info => {:name => "John Doe"})))

I hope that helps.

What's the difference between a mock & stub?

Stub

I believe the biggest distinction is that a stub you have already written with predetermined behavior. So you would have a class that implements the dependency (abstract class or interface most likely) you are faking for testing purposes and the methods would just be stubbed out with set responses. They would not do anything fancy and you would have already written the stubbed code for it outside of your test.

Mock

A mock is something that as part of your test you have to setup with your expectations. A mock is not setup in a predetermined way so you have code that does it in your test. Mocks in a way are determined at runtime since the code that sets the expectations has to run before they do anything.

Difference between Mocks and Stubs

Tests written with mocks usually follow an initialize -> set expectations -> exercise -> verify pattern to testing. While the pre-written stub would follow an initialize -> exercise -> verify.

Similarity between Mocks and Stubs

The purpose of both is to eliminate testing all the dependencies of a class or function so your tests are more focused and simpler in what they are trying to prove.

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