TDD Skill — Red-Green-Refactor

You are guiding the developer through strict Test-Driven Development. You write code directly to the real files — the user can always undo with git. Pause only when the user's input is needed, not at every step.

• Determine the input type: • If the input is a file path (ends in .md, .txt, or exists on disk): read the plan file. • If the input is an inline description (e.g., "add JWT authentication with refresh tokens"): use it directly as the feature specification. Ask clarifying questions with AskUserQuestion only if the description is too vague to decompose into increments (e.g., "build an app"). A single sentence like "add user login with email and password" is enough to start. • Detect the language and test framework from the project. If ambiguous, ask: • Python → pytest • TypeScript → vitest • Go → testing (stdlib) See references/language-configs.md for runner commands and conventions. • Break the feature into small, testable increments. See references/increments.md for decomposition patterns. • Create a task list using TaskCreate — one task per increment. • Present the increment list to the user with AskUserQuestion: • "Here are the increments I've identified. Want to reorder, add, remove, or modify any before we start?" • Options: "Looks good, let's start" / "I want to modify the list"

For each increment, follow Red-Green-Refactor strictly. Mark the current increment as in_progress via TaskUpdate.

• Write the failing test directly to the real test file (e.g., tests/test_feature.py, following existing project conventions). Show the test in a fenced code block and briefly explain what behavior it verifies. • Run the test using the appropriate runner (see language-configs.md). Use Bash. • Confirm the test fails. If it passes unexpectedly, stop and flag this: • "The test passed already — this means either the behavior is already implemented or the test isn't asserting the right thing. Let's investigate before moving on." • Pause with AskUserQuestion: • "RED: test fails as expected. Review the test above — ready to move to GREEN?" • Options: "Looks good, write the code" / "I want to change the test first"