🔁 Test-Driven Development (TDD)¶
TDD is a workflow where you write tests before implementation code. The goal is not "more tests", but better feedback and better design.
✅ The TDD Cycle: Red → Green → Refactor¶
1) Red: write a failing test that describes a small behavior 2) Green: implement the simplest code that makes the test pass 3) Refactor: improve code structure without changing behavior
✅ When TDD Helps Most¶
- Business logic with many edge cases
- Code that should be stable over time
- When you want confidence to refactor
⚠️ Common Mistakes¶
- Writing huge tests first (too much at once)
- Testing implementation details instead of behavior
- Skipping refactoring (code becomes messy)
🔍 Key Takeaways¶
- TDD is about small steps.
- Each test should add a new behavior.
- Refactor with confidence after tests are green.