Test-Driven Development

Test first, then code: see the test fail, make it pass with the least code, then tidy up with the tests green.

Steps

1. Red. Write one test for one behavior. Give it a clear name and use the real code, not mocks.
2. Watch it fail. Run the project's test command. The test must fail because the behavior is missing, not because of a typo or a missing import. If it passes, it tests nothing new: change the test.
3. Green. Write the simplest production code that makes it pass. Add nothing the test does not need.
4. Watch it pass. Run the full suite. Every test passes, with no errors or warnings.
5. Refactor. Tidy names and remove duplication. Run the suite again.

Repeat for the next behavior.

Rules

• No production code without a failing test first. Code written before its test is deleted and written again from the test.
• A bug fix starts with a test that reproduces the bug.
• If the test is hard to write, the design is unclear: simplify the interface.
• When writing or changing a test, read references/writing-good-tests.md.

Before you report the work as done

• Each new behavior has a test that you saw fail first.
• The full suite passes on the final code.