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An alternative approach to structuring your tests in XUnit

I typically write my unit tests using the AAA(Arrange-Act-Assert) pattern. This pattern splits a test in 3 sections:

  • The Arrange section of a unit test method initializes objects and sets the value of the data that is passed to the method under test.
  • The Act section invokes the method under test with the arranged parameters.
  • The Assert section verifies that the action of the method under test behaves as expected.

Here is an example from one of my projects using XUnit:

In the example above you can see that I include the 3 sections of the AAA pattern inside the test method itself.

Recently I was reading a blog post by Jeremy Miller where I noticed he was using a different approach to separate the 3 sections:

In the example above, Jeremy is using the IAsyncLifetime feature of XUnit to split the 3 sections:

This also works when you don't need async logic by using the constructor and the regular IDisposable interface:

What I like about this approach is that you have less repetitive code as the same arrange and act code can be used for multiple asserts. It allows you to easily group your test by test scenario and bring them logically together in one test class.

And as a nice bonus, it also solves the problem of finding good names for your test classes!

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