I just tried what you proposed (passing `null` everywhere) and I got 4 failing tests:

* EqualsForwardsCorrectCallToComparers (1 test case)
* EqualsReturnsCorrectResultForComplexClass (3 test cases) 

I *can* actually include test(s) verifying the values of the method parameters passed to the Stubs (as you suggested [here](https://github.com/AutoFixture/AutoFixture/pull/129/files#r5054429)).