/implement

Make failing tests pass with minimal code.

Usage

/implement

The implementer will automatically find failing tests from the most recent /write-tests run.

When to Use

• After /write-tests has created failing tests
• When you have specific tests that need implementation
• Never before tests exist

When NOT to Use

• No failing tests exist (run /write-tests first)
• You want to add features not covered by tests
• You want to refactor (use /simplify instead)

What It Does

1. Finds the failing tests from /write-tests
2. Reads tests to understand requirements
3. Writes the minimum code to make tests pass
4. Runs tests after each change
5. Stops when ALL tests pass

Output

The implementer agent will produce:

## Implementation Complete

### Tests Passed
- `test_client_reset_returns_observation` ✓
- `test_client_step_advances_state` ✓
- `test_client_handles_invalid_action` ✓

### Changes Made
| File | Change |
|------|--------|
| `src/openenv/core/client.py` | Added `reset()` method |
| `src/openenv/core/client.py` | Added `step()` method |
| `src/openenv/core/client.py` | Added input validation |

### Verification

PYTHONPATH=src:envs uv run pytest tests/test_client.py -v All 3 tests passed

### Next Steps
- Mark todo as complete
- Consider `/simplify` if change was large
- Move to next pending todo

Rules

1. Read the failing tests first to understand exactly what’s needed
2. Write the MINIMUM code needed to pass tests
3. Run tests after each change to verify progress
4. Do NOT add extra features not covered by tests
5. Do NOT refactor existing code (that’s /simplify‘s job)
6. Stop when all tests pass

Anti-patterns (NEVER do these)

• Adding features not covered by tests
• Refactoring existing code
• Writing additional tests (that’s /write-tests‘s job)
• Over-engineering solutions
• Adding comments or documentation beyond what’s necessary
• “Improving” code that already works

Completion Criteria

Before returning, verify:

1. ALL tests pass
2. No new test failures introduced
3. Implementation is minimal and focused

Philosophy

The implementer is a “code machine” – it takes test specifications and produces the minimal code to satisfy them. This keeps implementations focused and prevents scope creep.

Think of it as TDD’s second phase: Red → Green → Refactor. You are “Green” – make tests pass, nothing more.