---
name: agent-tdd-implementer
description: "Implement scoped changes through test-driven development, minimal code, and regression verification."
license: MIT
---

# agent-tdd-implementer

<TDD-Principles>
  1. Establish Scope and Tests:
    - Review requirements, acceptance criteria, and affected contracts.
    - Identify observable behaviors, edge cases, and regression risks.
    - Preserve existing interfaces and avoid unrelated changes.

  2. Red — Write Failing Tests:
    - Create focused tests for one behavior at a time.
    - Verify each test fails for the expected reason before implementation.
    - Prefer deterministic tests with isolated external dependencies.

  3. Green — Implement Minimally:
    - Write only the production code necessary to pass the failing tests.
    - Follow existing project conventions and architectural boundaries.
    - Avoid speculative features, premature abstractions, and unrelated refactoring.

  4. Refactor — Preserve Behavior:
    - Improve clarity and structure without changing observable behavior.
    - Keep tests passing throughout refactoring.
    - Remove duplication only when justified by existing code.

  5. Verify and Report:
    - Run focused tests, relevant regression tests, and applicable quality checks.
    - Confirm acceptance criteria and compatibility requirements.
    - Report failures, untested behavior, and remaining risks explicitly.
</TDD-Principles>

<Output-Formation>
  ### Implementation Summary
  - **Status**: [COMPLETED | PARTIAL | BLOCKED]
  - **Changes**: [Concise implementation summary]

  ### TDD Cycle
  - **Red**: [Failing tests and expected failure]
  - **Green**: [Minimal implementation]
  - **Refactor**: [Behavior-preserving improvements, if any]

  ### Verification
  - **Tests**: [Executed tests and results]
  - **Checks**: [Lint, type checks, or build results]
  - **Acceptance**: [Verified acceptance criteria]

  ### Remaining Issues
  - **Limitations**: [Unverified behavior, blockers, or residual risks]
</Output-Formation>