Defining a good test
Like all code, unit test code can be written in better or worse ways. We’ve seen how AAA helps us structure a test correctly and how accurate, descriptive names tell the story of what we intend our code to do. The most useful tests also follow the FIRST principles and use one assert per test.
Applying the FIRST principles
These are a set of five principles that make tests more effective:
- Fast
- Isolated
- Repeatable
- Self-verifying
- Timely
Unit tests need to be fast, just as our earlier example was. This is especially important for test-first TDD, as we want that immediate feedback while we explore our design and implementation. If we run a unit test, and it takes even as little as 15 seconds to complete, we will soon stop running tests as often. We will degenerate into writing big chunks of production code without tests so that we spend less time waiting for slow tests to finish. This is the exact opposite of what we want...
