Tdd Green

TDD Green Phase Skill

Purpose

• Write the simplest code to make the failing test pass
• Do not modify tests in this phase
• No refactoring or generalization
• Commit after tests pass

Inputs

• Failing test id
• Skill and asset references
• Project code style patterns from .github/instructions/tdd-patterns.instructions.md
• Canonical GREEN style guide placeholder at .github/skills/tdd-green/assets/project-code-style-patterns.md

Outputs

• Changed production files
• Test pass summary

Steps

1. Load .github/skills/tdd-green/assets/project-code-style-patterns.md first, then load core asset files for minimal implementation, anti-patterns, and commit discipline
2. Check whether the RED test compiles.

• If the test references missing production symbols (types, methods, fields), the only allowed edit is the smallest possible compile-only stub — no behavior.
• Run the narrow test again. It must now compile and fail at runtime/assertion level before proceeding.
• This is the distinction between structural red (compile failure) and behavioral red (assertion failure). Both are RED; behavior must not be added until you are at behavioral red.

1. Judge the next GREEN move before editing production code.

• Ask whether the change is the dumbest possible thing that makes only the current test pass.
• If the change also solves untested cases, tries to generalize, or looks like the feature instead of the slice, it is too broad.
• Prefer a constant, hardcoded branch, or the narrowest exact-case behavior the current test demands.
• Do not move from behavioral red into generalized implementation just because the change is small.

1. Write minimal code to pass the test
2. Use tdd-test-run with a test_run_request contract whose expected result is

a passing narrow check for the protected test or slice

1. If the observed result does not match the expected GREEN outcome, revert only

the scoped production changes and return to the preceding GREEN decision point

1. Run the broader validation required by project policy through tdd-test-run

before reporting GREEN complete

1. Return contract output

Completion Checks

• Only minimal code added
• All tests pass
• No test or refactor changes

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: mrlarson2007
• Source: mrlarson2007/copilot-tdd-harness
• License: MIT

Install and usage instructions live in the source repository linked above.