Check several different example inputs in a single test?

Question

Let's say I want to write a function that validates an email address with a regex. I write a little test to check my function and write the actual function. Make it pass.

However, I can come up with a bunch of different ways to test the same function ([email protected]; [email protected]; test.test.com, etc).

Do I put all the incantations that I need to check in the same, single test with several ASSERTS or do I write a new test for every single thing I can think of?

Thanks!

Answer 1

Most testing frameworks now support some sort of data based testing to let you run the same test on multiple data sets.

See the ValuesAttribute in NUnit.

xUnit.net, MBUnit and others have similar methods.

Answer 2

Generally I create many different tests, and give each it's own name. For example let's say that there are 3 different regexes {A, B, & C} for matching an email address. The function checks the incoming email for a match and accepts the first match found.

I would have the following tests.

• ATypeEmailShouldMatchPatternA
• BTypeEmailShouldMatchPatternB
• CTypeEmailShouldMatchPatternC
• BadEmailShouldNotMatchAnyPattern
• EmailCompatibleWithPatternAAndPatternBShouldBeMatchedByA
• EmailCompatibleWithPatternAAndCShouldBeMatchedByA
• EmailCompatibleWithPatternBAndCShouldBeMatchedByB

Generally I'd put one assert in each test.

Sometimes, however, I'll put more than one assert in a test if the asserts are all checking different parts of the same thing. For example, let's say I have a function that finds all the emails matching pattern A. My test feeds in a list of emails but only one matches pattern A. The function returns a list, and I expect that list to have only one element in it. So I would assert two things:

1. That the list has one element in it.
2. That the one element is the email that matches pattern A.