implement

name	implement
description	This skill should be used when the user asks to "implement phase N", "implement task T001", "do TDD for phase", "implement T001-T009", or wants to execute tasks following strict TDD red-green-refactor workflow.

Implement

User Input

PHASE_OR_TASK = $ARGUMENT

Accept and use user input (ARGUMENT). Valid formats:

• A phase name (e.g., "Phase 1", "US1", "Phase 3")
• A specific task ID (e.g., "T001", "T017-T028")
• A task range (e.g., "T001-T009")

Context Loading

1. Identify the current feature ID from the git branch (e.g., feature/001-mcp-integration → 001-mcp-integration)
2. Find the feature folder: check backlog/plans/{feature-id}/ first, then backlog/plans/_completed/{feature-id}/
3. Read {feature-path}/tasks.md to get task list
4. Read specs/tests/{feature-id}.md if it exists

Phase Execution

If the input is a phase name:

Phase Entry: Spec Tests (RED)

• Find the phase's entry spec test task (e.g., "T016 [SPEC] Run spec tests for FR-3...")
• Run the spec tests specified in that task
• Expected: ALL FAIL (requirements not yet implemented)
• If any pass unexpectedly, report and ask user to verify

Task Execution Loop

• For each task in the phase:
  1. [TEST] tasks: Write failing tests first
     • Run tests: cargo test {module} --lib → expect FAIL (RED)
  2. [IMPL] tasks: Implement minimal code to pass tests
     • Run tests: cargo test {module} --lib → expect PASS (GREEN)
  3. [SPEC] tasks: Skip during main loop (handled at phase boundaries)
  4. Mark task as completed in tasks.md (check the box)
  5. Run make lint to ensure code quality
  6. Commit after each logical group of tasks (2-3 tasks)

Phase Exit: Spec Tests (GREEN)

• Find the phase's exit spec test task (e.g., "T029 [SPEC] Run spec tests for FR-3...")
• Run the spec tests specified in that task
• Expected: ALL PASS (requirements satisfied)
• If any fail, identify which implementation tasks need revision

Task-Specific Execution

If the input is a task ID or range:

1. Read the task description from tasks.md
2. Check dependencies (if task has prerequisites, verify they're completed)
3. Execute based on task type:
   • [TEST]: Write tests, run them → expect FAIL
   • [IMPL]: Implement code, run tests → expect PASS
   • [SPEC]: Run spec tests as specified in task description
4. Mark task as completed in tasks.md
5. Run make check && make lint to verify

TDD Rules

For Rust code, strictly follow Red-Green-Refactor:

1. RED: Write failing test first → run cargo test → see failure
2. GREEN: Write minimal code to pass → run cargo test → see pass
3. REFACTOR: Clean up code → run cargo test → keep passing

For bash/scripts, implement directly without TDD.

Extensive Mocking Detection

STOP and ask the user when a [TEST] task would require:

• Mocking an entire external system (MCP server, database, HTTP server)
• Creating complex fake implementations with multiple methods/traits
• Spawning actual processes or network connections in unit tests
• More than 50 lines of mock/stub code to test a single function

Signs you're over-mocking:

• The mock is as complex as the real implementation
• Simulating protocol handshakes or connection lifecycle is required
• Tests require async runtime setup for fake services
• Mock state management becomes a testing problem itself

When detected, ask the user:

⚠️ Task {TASK_ID} requires extensive mocking to unit test.

The test would need to mock: {what needs mocking}

Options:
1. **Defer to integration test** - Implement first, test with real/echo server later
2. **Simplify test scope** - Test only pure functions, defer interaction tests
3. **Proceed with mocking** - Accept complexity, write the mock

Which approach do you prefer?

Typical resolution:

• Change [TEST] task to [INTEG] and move to integration phase
• Implement the code first, then write integration tests with real servers
• Update tasks.md to reflect the change

Verification

Before marking phase complete:

• All unit tests pass: make test-{module}
• All spec tests pass: python specs/tests/run_tests_claude.py specs/tests/{feature-id}.md
• Linting passes: make lint
• Build succeeds: make build

Finally (REQUIRED)

After implementation is complete, follow in this order:

1. Run /progress to generate session log in .ai/YYYY-MM-DD/
2. Run /commit to commit any remaining changes
3. Close GitHub issue if specified

This step is mandatory - do not skip the progress log.

Example Usage

/implement "Phase 1"           # Implement entire Phase 1 (Setup)
/implement "US1"               # Implement User Story 1 phase
/implement "T001"              # Implement single task
/implement "T017-T028"         # Implement task range