Test-Driven Development (TDD)

TDD is a development workflow where you write tests before implementing functionality.

The Cycle

1. Red: write a failing test for the desired behavior.
2. Green: implement the minimal code to pass the test.
3. Refactor: clean up while keeping tests green.

Benefits and Trade-offs

• Encourages small incremental design and good test coverage.
• Can slow initial development and may encourage over-testing internal details.

Example (outline)

• Write assert add([1,2]) == 3 (failing).
• Implement def add(items): return sum(items).
• Refactor to handle edge cases and keep tests green.