[Rubycocoa-talk] Two tricks for using Spec::Mocks with RubyCocoa

[Aaron V. <gru...@gm...>]

Hi all, I'm not to reading this list, so hopefully this isn't already
a well-known fact, but I wanted to share a trick that I spent a few
brain cells discovering:

I've been using Dr. Nic's rbiphonetest <
http://drnicwilliams.com/2008/07/04/unit-testing-iphone-apps-with-ruby-rbiphonetest/
> to write rspec specs and stories for an obj-c cocoa app.  I came
across two problems when trying to use mock objects to test obj-c
classes.

1)
    aMock = mock("a");
    aMock.stub!(:methodThatReturnsInt).and_return(42);

In this case (and I don't claim to understand what's behind the
scenes), the 42 gets cast incorrectly when it's passed off to obj-c,
since rubycocoa thinks it's returning an object instead of an int.
The solution:

    class MockA < OSX::NSObject
        objc_method :methodThatReturnsInt, "i@:"
    end
    aMock = mock("a");
    aMock.stub!(:methodThatReturnsInt).and_return(42);


2)
    aMock = mock("a");  # This is a mock of an obj-c class, OSX::A
    aMock.stub!(:methodThatReturnsInt).and_return(42);
    OSX::MyObjCClass.alloc.init.doSomethingWithA(aMock);

This is only a problem if MyObjCClass has some logic in it that is
checking [aMock isKindOfClass:[A class]].  But here's a way to work
around it and make a Spec::Mocks object that obj-c thinks is a
subclass of MyObjCClass.  The trick is to create a subclass of
MyObjCClass and then reimplement all it's methods to call
super.super.method so that the call will eventually get back to
Spec::Mocks' monkey-patching and our stubs and should_receive's will
work.

    class MockA < OSX::A
      def methodThatReturnsInt
        return super.super.methodThatReturnsInt
      end
    end
    aMock = mock("a");
    aMock.stub!(:methodThatReturnsInt).and_return(42);
    OSX::MyObjCClass.alloc.init.doSomethingWithA(aMock);

And now we can write specs for obj-c code that calls isKindOfClass: !
(Note that the previous objc_method trick is no longer necessary.)

===

That's all!  I hope someone finds this interesting or useful.  I'd
also appreciate any alternative suggestions from those who have inner
knowledge of rubycocoa or rspec.

Cheers,
--Aaron V.