TDD Workflow

> Write tests first, code second.

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1. The TDD Cycle

🔴 RED → Write failing test
    ↓
🟢 GREEN → Write minimal code to pass
    ↓
🔵 REFACTOR → Improve code quality
    ↓
   Repeat...

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2. The Three Laws of TDD

1.Write production code only to make a failing test pass

2.Write only enough test to demonstrate failure

3.Write only enough code to make the test pass

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3. RED Phase Principles

What to Write

| Focus | Example |

|-------|---------|

| Behavior | "should add two numbers" |

| Edge cases | "should handle empty input" |

| Error states | "should throw for invalid data" |

RED Phase Rules

●Test must fail first

●Test name describes expected behavior

●One assertion per test (ideally)

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4. GREEN Phase Principles

Minimum Code

| Principle | Meaning |

|-----------|---------|

| YAGNI | You Aren't Gonna Need It |

| Simplest thing | Write the minimum to pass |

| No optimization | Just make it work |

GREEN Phase Rules

●Don't write unneeded code

●Don't optimize yet

●Pass the test, nothing more

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5. REFACTOR Phase Principles

What to Improve

| Area | Action |

|------|--------|

| Duplication | Extract common code |

| Naming | Make intent clear |

| Structure | Improve organization |

| Complexity | Simplify logic |

REFACTOR Rules

●All tests must stay green

●Small incremental changes

●Commit after each refactor

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6. AAA Pattern

Every test follows:

| Step | Purpose |

|------|---------|

| Arrange | Set up test data |

| Act | Execute code under test |

| Assert | Verify expected outcome |

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7. When to Use TDD

| Scenario | TDD Value |

|----------|-----------|

| New feature | High |

| Bug fix | High (write test first) |

| Complex logic | High |

| Exploratory | Low (spike, then TDD) |

| UI layout | Low |

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8. Test Prioritization

| Priority | Test Type |

|----------|-----------|

| 1 | Happy path |

| 2 | Error cases |

| 3 | Edge cases |

| 4 | Performance |

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9. Anti-Patterns

| ❌ Don't | ✅ Do |

|----------|-------|

| Skip the RED phase | Watch test fail first |

| Write tests after | Write tests before |

| Over-engineer initial | Keep it simple |

| Multiple asserts | One behavior per test |

| Test implementation | Test behavior |

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10. AI-Augmented TDD

Multi-Agent Pattern

| Agent | Role |

|-------|------|

| Agent A | Write failing tests (RED) |

| Agent B | Implement to pass (GREEN) |

| Agent C | Optimize (REFACTOR) |

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> Remember: The test is the specification. If you can't write a test, you don't understand the requirement.

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