You find an error during FunctionalTest''''''ing. Rather than just fix it, you:
	* Pinpoint it in the code
	* Write the unit test that doesn't run, but if it did you believe the functional error will be resolved
	* Make the UnitTest work
	* Re-run the FunctionalTest to be sure the error is resolved

This is better than simply fixing the FunctionalTest, because:
	1. You are more focused when fixing the defect. You have to make a specific, concrete hypothesis about the source of the error. You can't just go around adding one and negating until the functional test runs.
	2. You now have a UnitTest (likely to be run more often than a FunctionalTest) that will blow up if the error recurs

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CategoryTesting