\cite[S. ix]{Beck2003} In TDD, we

• write new code only if an automated test has failed
• eliminate duplication.

The TDD mantra \cite[S. x]{Beck2003}

1. red: write a little test that doesn't work, and perhaps doesn't even compile at first.
2. green: make the test work quickly, committing whatever sins necessary in the process.
3. refactor: eliminate all of the duplication created in merely getting the test to work.

The rhythm of TDD \cite[S. 1]{Beck2003}

1. quickly add a test
2. run all tests and see the new one fail
3. make a little change
4. run all tests and see them all succeed
5. refactor to remove duplication