F.I.R.S.T. Unit Tests

• F.I.R.S.T. Unit Tests
  • Fast
  • Isolated
  • Repeatable
  • Self-Validating
  • Thorough / Timely

Fast

• Problem should be reported fast
• When tests are slow, developer tend to ignore them and then introduce bugs

Isolated

• 1 test = 1 case
• Order independent : Tests should not rely on the order of execution
• State independent : Tests should avoid to share state or data. Use init helpers to reduce code repetition if needed

Repeatable

• Deterministic (i.e. avoid Date and random)
• Environment independent : Running tests should have always same results different environments (CI, desktop, etc)

Self-Validating

• No manual inspection to check whether the test has passed or failed.

Thorough / Timely

• Write a test before writing corresponding code. It will produce code with easier testability.
• Cover all use cases better than Cover all code
• Cover boundary values and edge cases
• Cover errors and exceptions
• Cover bad inputs