MEPX
Chapter 3 of 10All chapters
  1. 1Why test
  2. 2Kinds of test
  3. 3What a good test looks like
  4. 4Fakes, stubs and mocks
  5. 5Coverage and flakiness
  6. 6Reproducing a bug
  7. 7Narrowing it down
  8. 8Reading the evidence
  9. 9Debuggers and tools
  10. 10The hard ones

Chapter 3 of 10

What a good test looks like

Readable, isolated, deterministic.

The qualities

Arrange, act, assert. One reason to fail. A name that says what behaviour is expected, so a red test tells you what broke without opening the file.

  • Test behaviour through the public interface, not private internals.
  • Avoid logic in tests: an if statement in a test is a bug waiting to happen.

Determinism

A test that depends on the clock, the network, random values or the order of other tests will eventually lie. Inject those dependencies so the test controls them.