cf-tdd

name	cf-tdd
description	Use when writing new production code, adding features, implementing changes, or refactoring existing code — e.g. "implement this", "build this feature", "create a function", "add a new endpoint", "write the implementation", "refactor this", "clean up this code", "extract into a module", "simplify this function", "scaffold", "write a test", "add tests", "create a component", "implement the API", "add a route", "write a service", "create the handler". Also auto-invoke when the conversation transitions from planning/discussion to actual code writing — any time production code is about to be written, this skill MUST be loaded first. By default uses direct implementation (no new tests written). TDD is enabled when `--add-tests` is present or config `tdd: true`. This is the gate for all code writing in the project. Do NOT auto-invoke for documentation-only changes, config edits, non-code file updates, or when the user is only asking questions about code without requesting changes.
created	2026-02-17T00:00:00.000Z
updated	2026-07-04T00:00:00.000Z

Implementation Workflow

CLI Requirement: NONE — Works without coding-friend-cli. See CLI requirements for the full matrix.

Custom Guide

Custom guide — auto-loaded below (if the raw command shows instead of its output, run it yourself):

bash "${PLUGIN_ROOT}/lib/load-custom-guide.sh" cf-tdd

If output is not empty, integrate returned sections: ## Before → before first step, ## Rules → apply throughout, ## After → after final step.

Mode Detection

Determine the implementation mode BEFORE doing anything else:

1. Check if the user's invocation or task description contains --add-tests
2. Check if .coding-friend/config.json exists and has "tdd": true
3. Check if the user's invocation or task description contains --auto (orthogonal to mode — autopilot can combine with both Direct and TDD mode).

Result:

• --add-tests present OR tdd: true in config → TDD mode. Show: > TDD mode enabled — RED → GREEN → REFACTOR. → TDD mode: Read ${PLUGIN_ROOT}/skills/cf-tdd/modes/tdd-mode.md now and follow RED→GREEN→REFACTOR.
• Neither → Direct mode (default). Show: > Direct mode — implementing without new tests
• Additionally, if --auto is present → Autopilot active. Show: > 🤖 Autopilot enabled — will auto-review, auto-fix Critical+Important, and auto-commit after implementation.

Skip Conditions

Check these BEFORE starting. If a skip condition is met, bypass the workflow entirely and proceed directly to implementation.

Auto-skip whitelist

If ALL changed/new files match these extensions, skip entirely — note why and proceed:

• Styles: .css, .scss, .sass, .less, .styl
• Docs: .md, .mdx, .txt, .rst
• Config: .json, .yaml, .yml, .toml, .env, .ini, .lock, .config

--no-tdd flag

Deprecated — direct mode is now the default. If present, acknowledge and proceed in direct mode:

--no-tdd is now the default. Proceeding in direct mode.

--auto flag

Note: --auto enables the Autopilot Post-Implementation Loop. It does NOT change the implementation mode itself. → When --auto is active, Read ${PLUGIN_ROOT}/skills/cf-tdd/modes/autopilot-loop.md now and run that loop instead of the standard Review Reminder.

---

Direct Mode (default)

1. Read the task description and relevant existing code
2. Implement the feature directly — no test writing
3. Run existing tests if a test suite exists — fix failures before reporting
4. Run typecheck/lint if available
5. Report what was implemented

Subagent Dispatch

For substantial implementations (new feature spanning 3+ files, complex algorithm, or multi-step feature), dispatch the cf-implementer agent instead of implementing inline. This preserves the main conversation's context.

Context Handoff Protocol

Before dispatching, create a structured context file for the agent:

1. Generate a task-id: use format <timestamp>-<short-descriptor> (e.g., 1717500000-add-auth-middleware)
2. Determine docsDir: read from .coding-friend/config.json if present, default to docs
3. Context file path: {docsDir}/context/{task-id}.json

If dispatching cf-explorer or cf-planner first, pass the context file path so they write their findings to it. The cf-implementer will then read and consume the same file.

Dispatch

Spawn the cf-implementer custom agent. Pass:

• Task description and expected behavior
• --add-tests in the prompt if TDD mode is active
• Context file path (if cf-explorer/cf-planner wrote one)
• Relevant file paths (source files, test files, config)
• Test framework and patterns used in the project (if TDD mode)
• Any constraints or edge cases

Prompt template:

Implement the following [--add-tests if TDD mode]:

Task: [description] Context file: [path to docs/context/.json, or "none"] Expected behavior: [what the code should do] Relevant files: [paths] Test patterns: [framework, conventions, example test file — only if TDD mode] Constraints: [any limits or edge cases]

Autopilot note: If cf-tdd was invoked with --auto, do NOT include --auto in the cf-implementer dispatch prompt. cf-implementer just executes a single task; the review/fix/commit loop is handled at this (cf-tdd) level.

Retry on Failure

After the cf-implementer returns, parse the last non-empty line of its response for the result signal using a strict regex match — ^\[CF-RESULT: (success|failure)( .*)?\]$:

• [CF-RESULT: success] → proceed to Review Reminder
• [CF-RESULT: failure] <reason> → trigger retry (see below)
• Sentinel missing, malformed, or not on the last non-empty line → treat as failure with reason empty-output. Never assume silent success — a truncated or aborted agent run may produce output that looks complete but skipped the result signal.

Retry protocol (max 1 retry):

1. Notify the user (always visible — never retry silently):

   > ⟳ Attempt 1 failed (<reason>). Retrying with error context...
   

2. Update the context file — write the failure details to {docsDir}/context/{task-id}.json:

   {
     "task_id": "<task-id>",
     "task_summary": "<original task>",
     "relevant_files": ["..."],
     "key_findings": ["..."],
     "constraints": ["..."],
     "suggested_approach": "...",
     "previous_failure": {
       "reason": "<tests-failed|compile-error|empty-output>",
       "error_summary": "<brief error details from the agent's response>",
       "attempt": 1
     }
   }
   

3. Re-dispatch cf-implementer with the updated context file path and an amended prompt:

When NOT to dispatch (implement inline instead):

• Single-file changes or small functions
• Pure refactoring with existing test coverage
• When the user is actively pairing on the implementation

Review Reminder

After implementation is complete: if --auto is active, the Autopilot Post-Implementation Loop in ${PLUGIN_ROOT}/skills/cf-tdd/modes/autopilot-loop.md has already handled review and commit — skip this section. Otherwise, ask the user if they want to run $cf-review or $cf-commit. Do NOT auto-run — wait for their choice.