TDD Cycle
System Prompt
⚠️ EXECUTION DIRECTIVE: When the user invokes this command, you MUST:
- IMMEDIATELY execute - no questions, no explanations first
- ALWAYS show full output from script/tool execution
- ALWAYS provide summary after execution completes
DO NOT:
- Say "I don't need to take action" - you ALWAYS execute when invoked
- Ask for confirmation unless
requires_confirmation: truein frontmatter - Skip execution even if it seems redundant - run it anyway
The user invoking the command IS the confirmation.
Usage
# Start TDD cycle for a feature
/tdd-cycle "user registration service"
# TDD with incremental test-by-test approach
/tdd-cycle --incremental "payment processor"
# TDD with full test suite approach
/tdd-cycle --suite "order management module"
# TDD for API endpoint
/tdd-cycle "REST API for product catalog"
Execute a comprehensive Test-Driven Development (TDD) workflow with strict red-green-refactor discipline:
[Extended thinking: This workflow enforces test-first development through coordinated agent orchestration. Each phase of the TDD cycle is strictly enforced with fail-first verification, incremental implementation, and continuous refactoring. The workflow supports both single test and test suite approaches with configurable coverage thresholds.]
Configuration
Coverage Thresholds
- Minimum line coverage: 80%
- Minimum branch coverage: 75%
- Critical path coverage: 100%
Refactoring Triggers
- Cyclomatic complexity > 10
- Method length > 20 lines
- Class length > 200 lines
- Duplicate code blocks > 3 lines
Phase 1: Test Specification and Design
1. Requirements Analysis
- Use Task tool with subagent_type="comprehensive-review::architect-review"
- Prompt: "Analyze requirements for: $ARGUMENTS. Define acceptance criteria, identify edge cases, and create test scenarios. Output a comprehensive test specification."
- Output: Test specification, acceptance criteria, edge case matrix
- Validation: Ensure all requirements have corresponding test scenarios
2. Test Architecture Design
- Use Task tool with subagent_type="unit-testing::test-automator"
- Prompt: "Design test architecture for: $ARGUMENTS based on test specification. Define test structure, fixtures, mocks, and test data strategy. Ensure testability and maintainability."
- Output: Test architecture, fixture design, mock strategy
- Validation: Architecture supports isolated, fast, reliable tests
Phase 2: RED - Write Failing Tests
3. Write Unit Tests (Failing)
- Use Task tool with subagent_type="unit-testing::test-automator"
- Prompt: "Write FAILING unit tests for: $ARGUMENTS. Tests must fail initially. Include edge cases, error scenarios, and happy paths. DO NOT implement production code."
- Output: Failing unit tests, test documentation
- CRITICAL: Verify all tests fail with expected error messages
4. Verify Test Failure
- Use Task tool with subagent_type="tdd-workflows::code-reviewer"
- Prompt: "Verify that all tests for: $ARGUMENTS are failing correctly. Ensure failures are for the right reasons (missing implementation, not test errors). Confirm no false positives."
- Output: Test failure verification report
- GATE: Do not proceed until all tests fail appropriately
Phase 3: GREEN - Make Tests Pass
5. Minimal Implementation
- Use Task tool with subagent_type="backend-development::backend-architect"
- Prompt: "Implement MINIMAL code to make tests pass for: $ARGUMENTS. Focus only on making tests green. Do not add extra features or optimizations. Keep it simple."
- Output: Minimal working implementation
- Constraint: No code beyond what's needed to pass tests
6. Verify Test Success
- Use Task tool with subagent_type="unit-testing::test-automator"
- Prompt: "Run all tests for: $ARGUMENTS and verify they pass. Check test coverage metrics. Ensure no tests were accidentally broken."
- Output: Test execution report, coverage metrics
- GATE: All tests must pass before proceeding
Phase 4: REFACTOR - Improve Code Quality
7. Code Refactoring
- Use Task tool with subagent_type="tdd-workflows::code-reviewer"
- Prompt: "Refactor implementation for: $ARGUMENTS while keeping tests green. Apply SOLID principles, remove duplication, improve naming, and optimize performance. Run tests after each refactoring."
- Output: Refactored code, refactoring report
- Constraint: Tests must remain green throughout
8. Test Refactoring
- Use Task tool with subagent_type="unit-testing::test-automator"
- Prompt: "Refactor tests for: $ARGUMENTS. Remove test duplication, improve test names, extract common fixtures, and enhance test readability. Ensure tests still provide same coverage."
- Output: Refactored tests, improved test structure
- Validation: Coverage metrics unchanged or improved
Phase 5: Integration and System Tests
9. Write Integration Tests (Failing First)
- Use Task tool with subagent_type="unit-testing::test-automator"
- Prompt: "Write FAILING integration tests for: $ARGUMENTS. Test component interactions, API contracts, and data flow. Tests must fail initially."
- Output: Failing integration tests
- Validation: Tests fail due to missing integration logic
10. Implement Integration
- Use Task tool with subagent_type="backend-development::backend-architect"
- Prompt: "Implement integration code for: $ARGUMENTS to make integration tests pass. Focus on component interaction and data flow."
- Output: Integration implementation
- Validation: All integration tests pass
Phase 6: Continuous Improvement Cycle
11. Performance and Edge Case Tests
- Use Task tool with subagent_type="unit-testing::test-automator"
- Prompt: "Add performance tests and additional edge case tests for: $ARGUMENTS. Include stress tests, boundary tests, and error recovery tests."
- Output: Extended test suite
- Metric: Increased test coverage and scenario coverage
12. Final Code Review
- Use Task tool with subagent_type="comprehensive-review::architect-review"
- Prompt: "Perform comprehensive review of: $ARGUMENTS. Verify TDD process was followed, check code quality, test quality, and coverage. Suggest improvements."
- Output: Review report, improvement suggestions
- Action: Implement critical suggestions while maintaining green tests
Incremental Development Mode
For test-by-test development:
- Write ONE failing test
- Make ONLY that test pass
- Refactor if needed
- Repeat for next test
Use this approach by adding --incremental flag to focus on one test at a time.
Test Suite Mode
For comprehensive test suite development:
- Write ALL tests for a feature/module (failing)
- Implement code to pass ALL tests
- Refactor entire module
- Add integration tests
Use this approach by adding --suite flag for batch test development.
Validation Checkpoints
RED Phase Validation
- All tests written before implementation
- All tests fail with meaningful error messages
- Test failures are due to missing implementation
- No test passes accidentally
GREEN Phase Validation
- All tests pass
- No extra code beyond test requirements
- Coverage meets minimum thresholds
- No test was modified to make it pass
REFACTOR Phase Validation
- All tests still pass after refactoring
- Code complexity reduced
- Duplication eliminated
- Performance improved or maintained
- Test readability improved
Coverage Reports
Generate coverage reports after each phase:
- Line coverage
- Branch coverage
- Function coverage
- Statement coverage
Failure Recovery
If TDD discipline is broken:
- STOP immediately
- Identify which phase was violated
- Rollback to last valid state
- Resume from correct phase
- Document lesson learned
TDD Metrics Tracking
Track and report:
- Time in each phase (Red/Green/Refactor)
- Number of test-implementation cycles
- Coverage progression
- Refactoring frequency
- Defect escape rate
Anti-Patterns to Avoid
- Writing implementation before tests
- Writing tests that already pass
- Skipping the refactor phase
- Writing multiple features without tests
- Modifying tests to make them pass
- Ignoring failing tests
- Writing tests after implementation
Success Criteria
- 100% of code written test-first
- All tests pass continuously
- Coverage exceeds thresholds
- Code complexity within limits
- Zero defects in covered code
- Clear test documentation
- Fast test execution (< 5 seconds for unit tests)
Notes
- Enforce strict RED-GREEN-REFACTOR discipline
- Each phase must be completed before moving to next
- Tests are the specification
- If a test is hard to write, the design needs improvement
- Refactoring is NOT optional
- Keep test execution fast
- Tests should be independent and isolated
TDD implementation for: $ARGUMENTS
Action Policy
<default_behavior> This command implements changes by default when user intent is clear. Proceeds with:
- Code generation/modification
- File creation/updates
- Configuration changes
- Git operations (if applicable)
Provides concise progress updates during execution. </default_behavior>
Success Output
When TDD cycle completes:
✅ COMMAND COMPLETE: /tdd-cycle
Feature: <feature-name>
Mode: <incremental|suite>
Phases: RED ✓ GREEN ✓ REFACTOR ✓
Tests: N written, M passing
Coverage: XX%
Quality: Complexity within limits
Completion Checklist
Before marking complete:
- RED phase: All tests fail correctly
- GREEN phase: All tests pass
- REFACTOR phase: Code quality improved
- Coverage exceeds threshold
- Complexity within limits
Failure Indicators
This command has FAILED if:
- ❌ Tests written after implementation
- ❌ Tests modified to pass
- ❌ Coverage below threshold
- ❌ Refactor phase skipped
When NOT to Use
Do NOT use when:
- Fixing urgent production bug
- Exploratory prototyping
- Trivial one-line changes
Anti-Patterns (Avoid)
| Anti-Pattern | Problem | Solution |
|---|---|---|
| Write code first | Not TDD | Always write test first |
| Skip refactor | Accumulates debt | Refactor is mandatory |
| Modify failing tests | False coverage | Keep original test intent |
Principles
This command embodies:
- #2 First Principles - Test defines behavior
- #3 Complete Execution - All 3 phases
Full Standard: CODITECT-STANDARD-AUTOMATION.md