Chapter 4 - Building Tests

To do refactoring properly, I need a solid suite of tests to spot my inevitable mistakes.

The Value of Self-Testing Code

• make sure all tests are fully automatic and that they check their own results
• a suite of tests is a powerful bug detector that decapitates the time it takes to find bugs

If you want to refactor, you have to write tests

A First Test

• simplicity of feedback from tests. just dots
• personally like verbose test output

Add Another Test

Testing should be risk driven; remember, I'm trying to find bugs, now or in the future. Therefore I don't test accessor methods that just read and write a field. They are so simple that I'm not likely to find a bug there.

My focus is to test areas that I'm most worried about going wrong.

Probing the Boundaries

• Seeing what happens when things go wrong

Whenever I have a collection of something, ... I like to see what happens when it's empty

• What happens when negative numbers are passed to a function that expects positive numbers? Division by zero?
  How do you probe boundaries?

Much More Than This

When you get a bug report, start by writing a unit test that exposes the bug

Picks

• JP: Taking time off