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Discussion on: What are your tips and tricks for beginners writing tests?

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Austin S. Hemmelgarn •

Some general tips that I see a lot of developers miss:

  • Test to your defined API, and take the time to define things that your API consumers care about which are not explicitly defined. In essence, what matters is what you promise (via your API) to deliver, not the details that you don't call out. In short, test behavior, not implementation.
  • Properly categorize your testing. Specifically, differentiate between unit tests, integration tests, end to end tests, and stress/performance tests. Each type is important, and each has a different purpose, make sure you know what type of test each test you write is because that helps you understand better both how to write the test, and what you're actually testing.
  • Always leave stress/performance testing for last unless you have a clearly defined performance goal as an engineering requirement. Testing performance properly is seriously challenging, and often not very well supported, so unless you need these types of tests, they will usually end up being far more effort than they're worth.
  • Don't mix test types within a test case. This is mostly a sanity tip. Any time you try to mix testing types inside a test case, it gets harder to figure out what exactly you're testing. Simple cases that test only one thing in one way are the easiest to understand and work with.
  • Start with whatever type of testing your language/framework supports best, then cover the other types. Most languages or frameworks provide really good support for either unit testing or integration testing, and at best mediocre support for everything else. Always start with whatever type is best supported, as that will make writing the initial tests easy (and once you have those, it's easier to branch out into less well supported types of tests).
  • Make sure to test your error handling. I see lots of people over-look this regularly, and it's actually really important (if you're not handling errors correctly all kinds of nasty things can happen).