I have a question about unit testing. In general, should you try several values? I ask because in your example, you used addition for the Multiply() function to show a failing result.

But, what if you used Multiply(2, 2) and Assert.AreEqual(4, result)? The test would pass even if the code is wrong. I realize that in this simple example, it is easy to figure out that you shouldn't use 2 and 2, but in a more complex situation, I imagine it won't always be so obvious.

So, is it common testing practice to use more than one example test?

adimauro

Please note that Simone (the author of unit testing chapter) is on travel and it may take him a few days to respond.

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Keyvan Nayyeri

Antonio,
in general you should test a general case when you are doing the first tests (or when you are designing the application via TDD.
And then you usually need to test the boundaries cases or the the special cases.
Simo

It does bring up an important point. The purpose of TDD is to require you to do proper program development. Good requirements research, good architecture planning, etc. If you plan out your tests and find your boundary cases well, your tests will demonstrate when the code that you're writing is doing a great job or not. If you quickly dash off some haphazard tests however, you can get into all kinds of trouble. So TDD can't save you from bad programming, it just makes it more obvious when you do.

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