Is there a way to undo Mocha stubbing of any_instance in Test::Unit

Question

Much like this question, I too am using Ryan Bates's nifty_scaffold. It has the desirable aspect of using Mocha's any_instance method to force an "invalid" state in model objects buried behind the controller.

Unlike the question I linked to, I'm not using RSpec, but Test::Unit. That means that the two RSpec-centric solutions there won't work for me.

Is there a general (ie: works with Test::Unit) way to remove the any_instance stubbing? I believe that it's causing a bug in my tests, and I'd like to verify that.

Solution 1

As it happens, Mocha 0.10.0 allows unstubbing on any_instance().

str = "Not Stubbed!"
String.any_instance.stubs(:to_s).returns("Stubbed!")
puts str.to_s   # "Stubbed!"
String.any_instance.unstub(:to_s)
puts str.to_s   # "Not Stubbed!"

Solution 2

Mocha does not provide such a functionality. However you can implement it yourself.

The first thing we should know about mocha is that mocha actually replaces the original methods when you stub them. So in order to be able to restore these methods later, you must keep a reference to the former ones. It can be easily achieved by: alias new_method old_method. It must be done before mocking the old_method.

Now, to unmock a method, you only need to alias old_method new_method.

Consider the following code:

class A
    def a
        true
    end
end


class TestA < Test::Unit::TestCase
    def test_undo_mock
        a = A.new
        A.class_eval {alias unmocked_a a}

        A.any_instance.stubs(:a).returns("b")
        assert a.a, "b"

        A.class_eval {alias a unmocked_a}
        assert a.a, "a"
    end
end