/tdd - Test-Driven Development Workflow Strict TDD workflow: tests first, then implementation. When to Use "Implement X using TDD" "Build this feature test-first" "Write tests for X then implement" Any feature where test coverage is critical Bug fixes that need regression tests TDD Philosophy Overview Write the test first. Watch it fail. Write minimal code to pass. Core principle: If you didn't watch the test fail, you don't know if it tests the right thing. Violating the letter of the rules is violating the spirit of the rules. The Iron Law NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST Write code before the test? Delete it. Start over. No exceptions: Don't keep it as "reference" Don't "adapt" it while writing tests Don't look at it Delete means delete Implement fresh from tests. Period. Red-Green-Refactor RED - Write Failing Test Write one minimal test showing what should happen. Good: test ( 'retries failed operations 3 times' , async ( ) => { let attempts = 0 ; const operation = ( ) => { attempts ++ ; if ( attempts < 3 ) throw new Error ( 'fail' ) ; return 'success' ; } ; const result = await retryOperation ( operation ) ; expect ( result ) . toBe ( 'success' ) ; expect ( attempts ) . toBe ( 3 ) ; } ) ; Clear name, tests real behavior, one thing. Bad: test ( 'retry works' , async ( ) => { const mock = jest . fn ( ) . mockRejectedValueOnce ( new Error ( ) ) . mockResolvedValueOnce ( 'success' ) ; await retryOperation ( mock ) ; expect ( mock ) . toHaveBeenCalledTimes ( 3 ) ; } ) ; Vague name, tests mock not code. Requirements: One behavior Clear name Real code (no mocks unless unavoidable) Verify RED - Watch It Fail MANDATORY. Never skip. npm test path/to/test.test.ts

or

pytest path/to/test_file.py Confirm: Test fails (not errors) Failure message is expected Fails because feature missing (not typos) Test passes? You're testing existing behavior. Fix test. Test errors? Fix error, re-run until it fails correctly. GREEN - Minimal Code Write simplest code to pass the test. Good: async function retryOperation < T

( fn : ( ) => Promise < T

) : Promise < T

{ for ( let i = 0 ; i < 3 ; i ++ ) { try { return await fn ( ) ; } catch ( e ) { if ( i === 2 ) throw e ; } } throw new Error ( 'unreachable' ) ; } Just enough to pass. Bad: async function retryOperation < T

( fn : ( ) => Promise < T

, options ? : { maxRetries ? : number ; backoff ? : 'linear' | 'exponential' ; onRetry ? : ( attempt : number ) => void ; } ) : Promise < T

{ // YAGNI - over-engineered } Don't add features, refactor other code, or "improve" beyond the test. Verify GREEN - Watch It Pass MANDATORY. npm test path/to/test.test.ts Confirm: Test passes Other tests still pass Output pristine (no errors, warnings) Test fails? Fix code, not test. Other tests fail? Fix now. REFACTOR - Clean Up After green only: Remove duplication Improve names Extract helpers Keep tests green. Don't add behavior. Common Rationalizations Excuse Reality "Too simple to test" Simple code breaks. Test takes 30 seconds. "I'll test after" Tests passing immediately prove nothing. "Tests after achieve same goals" Tests-after = "what does this do?" Tests-first = "what should this do?" "Already manually tested" Ad-hoc ≠ systematic. No record, can't re-run. "Deleting X hours is wasteful" Sunk cost fallacy. Keeping unverified code is technical debt. "Keep as reference, write tests first" You'll adapt it. That's testing after. Delete means delete. "Need to explore first" Fine. Throw away exploration, start with TDD. "Test hard = design unclear" Listen to test. Hard to test = hard to use. "TDD will slow me down" TDD faster than debugging. Pragmatic = test-first. "Manual test faster" Manual doesn't prove edge cases. You'll re-test every change. Red Flags - STOP and Start Over Code before test Test after implementation Test passes immediately Can't explain why test failed Tests added "later" Rationalizing "just this once" "I already manually tested it" "Tests after achieve the same purpose" "Keep as reference" or "adapt existing code" All of these mean: Delete code. Start over with TDD. Verification Checklist Before marking work complete: Every new function/method has a test Watched each test fail before implementing Each test failed for expected reason (feature missing, not typo) Wrote minimal code to pass each test All tests pass Output pristine (no errors, warnings) Tests use real code (mocks only if unavoidable) Edge cases and errors covered Can't check all boxes? You skipped TDD. Start over. When Stuck Problem Solution Don't know how to test Write wished-for API. Write assertion first. Ask your human partner. Test too complicated Design too complicated. Simplify interface. Must mock everything Code too coupled. Use dependency injection. Test setup huge Extract helpers. Still complex? Simplify design. Workflow Execution Workflow Overview ┌────────────┐ ┌──────────┐ ┌──────────┐ ┌───────────┐ │ plan- │───▶│ arbiter │───▶│ kraken │───▶│ arbiter │ │ agent │ │ │ │ │ │ │ └────────────┘ └──────────┘ └──────────┘ └───────────┘ Design Write Implement Verify approach failing minimal all tests tests code pass Agent Sequence

Agent Role Output 1 plan-agent Design test cases and implementation approach Test plan 2 arbiter Write failing tests (RED phase) Test files 3 kraken Implement minimal code to pass (GREEN phase) Implementation 4 arbiter Run all tests, verify nothing broken Test report Core Principle NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST Each agent follows the TDD contract: arbiter writes tests that MUST fail initially kraken writes MINIMAL code to make tests pass arbiter confirms the full suite passes Execution Phase 1: Plan Test Cases Task( subagent_type="plan-agent", prompt=""" Design TDD approach for: [FEATURE_NAME] Define: 1. What behaviors need to be tested 2. Edge cases to cover 3. Expected test structure DO NOT write any implementation code. Output: Test plan document """ ) Phase 2: Write Failing Tests (RED) Task( subagent_type="arbiter", prompt=""" Write failing tests for: [FEATURE_NAME] Test plan: [from phase 1] Requirements: - Write tests FIRST - Run tests to confirm they FAIL - Tests must fail because feature is missing (not syntax errors) - Create clear test names describing expected behavior DO NOT write any implementation code. """ ) Phase 3: Implement (GREEN) Task( subagent_type="kraken", prompt=""" Implement MINIMAL code to pass tests: [FEATURE_NAME] Tests location: [test file path] Requirements: - Write ONLY enough code to make tests pass - No additional features beyond what tests require - No "improvements" or "enhancements" - Run tests after each change Follow Red-Green-Refactor strictly. """ ) Phase 4: Validate Task( subagent_type="arbiter", prompt=""" Validate TDD implementation: [FEATURE_NAME] - Run full test suite - Verify all new tests pass - Verify no existing tests broke - Check test coverage if available """ ) TDD Rules Enforced arbiter cannot write implementation code kraken cannot add untested features Tests must fail before implementation Tests must pass after implementation Example User: /tdd Add email validation to the signup form Claude: Starting /tdd workflow for email validation... Phase 1: Planning test cases... [Spawns plan-agent] Test plan: - Valid email formats - Invalid email formats - Empty email rejection - Edge cases (unicode, long emails) Phase 2: Writing failing tests (RED)... [Spawns arbiter] ✅ 8 tests written, all failing as expected Phase 3: Implementing minimal code (GREEN)... [Spawns kraken] ✅ All 8 tests now passing Phase 4: Validating... [Spawns arbiter] ✅ 247 tests passing (8 new), 0 failing TDD workflow complete! Refactor Phase (Optional) After GREEN, you can add a refactor phase: Task( subagent_type="kraken", prompt=""" Refactor: [FEATURE_NAME] - Clean up code while keeping tests green - Remove duplication - Improve naming - Extract helpers if needed DO NOT add new behavior. Keep all tests passing. """ )