gotr | Off-the-record messaging for group conversations | Chat library

Writing unit tests is relatively easy. Writing good unit tests is hard. This isn't helped because we are introduced to unit testing with trivial code examples that don't mimic real life usage.

Try to avoid mocking unless you need to verify the invocations of a dependency. Prefer using stubs, fakes or real implementations. Knowing when to use each is a matter of experience and where the difficulty comes in. Also, think about your design. If you are finding it difficult to unit test, this could be because you need to redesign.

Unit tests take time to write and maintain. You will always be quicker writing code without unit tests. However, we write unit tests to give us some assurance that our code works correctly and confidence to re-factor.

Hence it's important to try to write the test against the behaviour (black box) instead of the implementation (white-box). This isn't always possible but unit tests that are tied to the implementation are fragile, discourage refactoring and can also sometimes mask unexpected behaviour.

Some unit testing resources worth reading:

1. Mocks Aren't Stubs
2. Testing on the Toilet Blog
3. TDD - Where it all went wrong

As way as an example, think of writing a unit test for a simple email address validator. We want to write a function that will take a string and return true/false based on whether a valid email address was supplied.

A trivial example implementation would be: