TDD Best Practices

Here’s a list of TDD best practices that I have been accumulating in my developer toolbox. Ping me if you think I’m missing anything, and I will add it to the list.

• Have separate source and test folders. Test code should follow the structure of source.
• Test should fail the first time it’s written/run
• Test names should reflect intent, and names should be expressive
• Refactor to remove duplicate code after passing test
• Re-run tests after every refactoring
• Only write new code when a test is failing. Each test should test new/different behavior.
• Write the assertion first
• Minimize the assertions in each test
• All tests should pass before writing the next test
• Only refactor when all tests are passing
• Write the simplest code to pass the test
• Don’t introduce dependencies between tests. Test should pass when run in any order.
• Tests should run fast. A slow test is a test that won’t get run.
• Use mock objects to test code at system boundaries (e.g. database, container, file system) so that tests run fast.