tdd-guide (Codex Compatibility)

Use this skill for all feature work, bug fixes, and refactors that change behavior.

Routing Boundary

Use this skill when the user wants to build or change behavior through tests:

• TDD / test-driven development
• write failing tests first
• test-first implementation
• RED -> GREEN -> REFACTOR

Do not use it when tests are already failing and the user wants root cause; route that to systematic-debugging. Do not use it when the user only wants a test/coverage report; route that to generating-test-reports.

Core Rule

No production code before a failing test.

Workflow

1. RED

• Write one failing test for one behavior.
• Confirm the failure is expected.

2. GREEN

• Implement the minimal code to pass.
• Re-run tests and keep scope narrow.

3. REFACTOR

• Improve structure/naming without changing behavior.
• Keep all tests green.

4. COVERAGE

• Verify coverage target (recommended >=80% for lines/functions/branches).
• Add missing tests for edge/error paths.

Minimum Test Set

• Unit: public functions and core logic.
• Integration: API/data/service boundaries.
• E2E: critical user path only when relevant.

Required Edge Cases

• Null/undefined input
• Empty values
• Invalid types
• Boundary values
• Error paths (network/DB/file)
• Concurrency-sensitive behavior

Vibe Integration

• Primary coding skill in M-grade flow.
• Compatible fallback target for .