GNU + Linux = broken development model

WHQL testing involves running Microsoft's test suite on your own system. If I remember correctly, they require you use an SMP system, x86-64 and >4GB RAM, which historically have exposed a number of driver bugs, and they test various corner cases in power management. But it's still possible to have the driver cheat to pass the tests, or to run the test suite repeatedly until it passes, or even modify the test suite to falsely report passes.