We came across a strange thing with the mock framework in PhpUnit .
We had some test code that created a mock for a Store class, and gave it a method to mock out:
$mockStore = $this->getMock('Store', array('save'));
That seemed to work fine in the tests, we could setup expectations, the correct return values got returned, and so on.
It turns out that the constructor for the Store class needed some parameters, and the mock framework needs you to supply those parameters when you create the mock, because it will call the real constructor behind the scenes.
The mock had been working OK previously because the real Store class hadn't been loaded anywhere by the test - but then the changes to some require_once statements elsewhere in the code meant that the Store class WAS now loaded, and instantiated by the call to create a mock.
So the mock framework in PhpUnit will create a mock for you even if it has no idea what class it is that you're trying to mock out - you could do
$mockStore = $this->getMock('foo', array('save'));
and it would still give you a mock that worked fine. If it DOES find a class of that name, though, it'll instantiate it.
In fact, this behaviour is probably a good thing for TDD - it means you can create the mocks you need before you've ever created the real classes. You just have to be aware that when you DO create the real class, the mocks will start being created based on the real thing.
The solution in our test was to use the flag that tells the mock framework not to call the original constructor - it's a bit more clumsy, because you also have to supply some other additional parameters:
$mockStore = $this->getMock('Store', array('save'), array(), '', FALSE);