tdd

name	tdd
description	Strict test-driven development workflow. Use when implementing any feature, bug fix, or code change. Follows RED → GREEN → REFACTOR cycle with stack-aware test runner detection. Triggers on: implement, build, create, add feature, fix bug, write code for.

TDD Workflow

Follow this cycle strictly for every code change.

Phase 1: RED (Failing Tests)

1. Read the spec or requirement thoroughly
2. Identify acceptance criteria and edge cases
3. Create test file(s) in the appropriate location:
   • .csproj/.sln → tests/Unit/ using xUnit + FluentAssertions
   • go.mod → *_test.go using testing + testify (table-driven)
   • Cargo.toml → #[cfg(test)] mod tests using built-in + tokio-test
   • pyproject.toml → tests/unit/test_*.py using pytest
   • package.json with react → *.test.tsx using Vitest + Testing Library
   • package.json with react-native → *.test.tsx using Jest + RNTL
   • Package.swift/.xcodeproj → *Tests.swift using XCTest
4. Write tests for: happy path, edge cases, error conditions
5. Run tests — confirm ALL FAIL
6. Commit: test(<scope>): add failing tests for <feature>

Phase 2: GREEN (Minimum Implementation)

1. Pick ONE failing test
2. Write the minimum code to make it pass
3. Run tests — confirm that test passes
4. Repeat for each failing test
5. Commit: feat(<scope>): implement <feature>

Phase 3: REFACTOR

1. Look for duplication, unclear naming, long functions (aim for < 20 lines)
2. Extract patterns, improve structure
3. Run tests after EACH change — must stay green
4. Commit: refactor(<scope>): improve <description>

Phase 4: Integration Tests

1. Write integration tests for component interactions
2. Use TestContainers for database tests
3. Test with real service boundaries (not mocks)
4. Commit: test(integration): add <feature> integration tests

Rules

• NEVER write production code without a failing test
• Each test tests ONE behavior
• Descriptive test names: should_<behavior>_when_<condition>
• If a test is hard to write, the design needs improvement
• If requirements are unclear, STOP and ask before writing tests