I’m a written-test-case hater.  That is to say, in general, I think writing detailed test cases is not a good use of tester time.  A better use is interacting with the product-under-test.

But something occurred to me today:

The value of a detailed test case increases if you don’t perform it and decreases when you do perform it.

• The increased value comes from mentally walking through the test, which forces you to consider as many details as you can without interacting with the product-under-test.  This is more valuable than doing nothing.
• The decreased value comes from interacting with the product-under-test, which helps you learn more than the test case itself taught you.

What’s the takeaway?  If an important test is too complicated to perform, we should at least consider writing a detailed test case for it.  If you think you can perform the test, you should consider not writing a detailed test case and instead focusing on the performance and taking notes to capture your learning as it occurs.