F.I.R.S.T. rules

Clean tests should follow the rules:

• Fast tests should be fast because we want to run them frequently.

• Independent tests should not depend on each other. They should provide same output whether run independently or all together in any order.

• Repeatable tests should be repeatable in any environment and there should be no excuse for why they fail.

• Self-Validating a test should answer with either Passed or Failed. You don’t need to compare log files to answer if a test passed.

• Timely unit tests should be written before the production code. If you write tests after the production code, you might find writing tests too hard.