Chapter 9 - Unit Tests

• 3 laws of Test Driven Development (TDD)

  1. You may not write production code without writting a failing unit test
  2. You may not write more of a unit test than is sufficient to fail
  3. You may not write more production code than is sufficient to pass the current failing test

• These laws lock you into a cycle of writting tests with production code

• Keep Tests Clean

  • Test should be at the same standard as production code
  • A messy test is the same as having no tests

• What Makes a Clean Tests:

  • High Readability
  • High Clarity
  • Simplicity
  • High Density of Expressions (say a lot with as few expressions)

• Have a Single Concept per Test

  • Don't have long test functions. We want to find quickly in our code where the problem is
  • Having a single assert per test is a good guideline to follow

• F.I.R.S.T

  • Clean Tests follow 5 other rules
    • Fast (Runs quickly)
    • Independant (One test doesn't rely on another)
    • Repeatable (Can be run in any enviroment)
    • Self validating (Boolean output, true or false)
    • Timely (written quickly, runs timely)