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Some general testing practices

• Martin Fowler says "Whenever you are tempted to type something into a print statement or a debugger expression, write it as a test case instead."
• At first you will have to create a lot of fixtures, but then you will find you have created all the infrastructure and new tests become easier to add.
• Try to write tests that you imagine to be useful. Look for the boundary cases.
• When to add tests:
  • During development: while you are designing your class (but before implementing).
  • During debugging: when someone discovers a defect, first write a test that should succeed if your program is working, then debug until it succeeds.
• When to run the tests:
  • All the time.
  • If you find newly introduced errors right away, then you have a good idea where the error might be.
  • Fix errors right away, keep your test suite running.

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