OCMock does not recognize called selector
===

I'm struggling with a testcase that uses OCMock. So far I used OCMock in a few projects and it always work as i thought. I have the following method that tests that `[self setNeedsDisplay]` is called when I set a property called `image`. 

    - (void)testSetTapColorCallsDrawRect 
    {
        SMColorButton *button = [[SMColorButton alloc] initWithImage:nil];
        id mock = [OCMockObject partialMockForObject:button];
    
        // Exptect setNeedsDisplay. 
        [[mock expect] setImage:OCMOCK_ANY];
        [[mock expect] setNeedsDisplay];
    
        button.image = [UIImage imageNamed:@"Button.png"];
    
        [mock verify];
    }

And the setter for the `image` property looks like this.

    - (void)setImage:(UIImage *)anImage
    {
        // Set the image if it changed.
        if (anImage != image) {
            image = anImage;
            [self setNeedsDisplay];
        }
    }

You can see `[self setNeedsDisplay]` is called in the setter. But when I run the tests I get the following error: 


`OCPartialMockObject[SMColorButton]: expected method was not invoked: setNeedsDisplay`

It looks as if the method was not called. But if I set a breakpoint the the setter method, it stops and shows me that the line was executed by the application. 

Can you help me out? I don't see what I'm doing wrong...
