tdd

TDD

Use this skill as a single-user workflow. Do not introduce worker, task assignment, or team coordination concepts.

Core Rules

• Read the request, relevant code, and constraints before implementing.
• Define what counts as done before writing production code.
• Prefer a red phase when the task supports automated tests.
• Do not default to E2E. Use E2E only when explicitly requested, already required by the task contract, or when lower-cost verification cannot cover the acceptance risk.
• If the task needs test-case design, regression planning, acceptance coverage, or broader QA execution, invoke qa-expert instead of expanding this skill into a full QA workflow.
• If automated tests are not appropriate, define manual verification before implementing.
• Do not treat the work as complete until verification finishes.
• If verification is skipped, state the reason and residual risk explicitly.

Workflow

Follow this sequence:

1. Read context
2. Define acceptance criteria
3. Write failing tests when feasible
4. Implement
5. Verify
6. Conclude

Do not skip ahead unless the previous step is clearly satisfied.

Step 1: Read Context

Inspect the request and the surrounding implementation before changing anything.

Confirm:

• goal
• scope
• constraints
• non-goals
• existing verification options

If the request is ambiguous, stop and resolve the ambiguity before continuing.

Step 2: Define Acceptance Criteria

Write acceptance criteria before implementation.

Cover:

• expected behavior
• edge cases
• failure cases
• observable completion conditions

If acceptance criteria cannot be written yet, the task is not ready for implementation.

Step 3: Write Failing Tests When Feasible

If the task supports automated verification, write or update tests before implementation.

Target a real red phase:

• new behavior is asserted
• current code fails that assertion
• expected outcome is clear

If automated tests are not a good fit, explicitly define the manual verification procedure before moving on.

Step 4: Implement

Implement against the acceptance criteria and verification plan.

Do not expand scope during implementation unless the acceptance criteria are updated first.

Step 5: Verify

Use the strongest available verification path in this order:

1. Existing automated tests
2. New automated tests added for the change
3. Repeatable manual verification with concrete steps and expected results
4. skipped only when verification is blocked in the current environment

E2E is not the default verification path. Prefer lower-cost checks first unless E2E is explicitly required or the acceptance risk cannot be covered otherwise.

If the task needs dedicated test-case design, regression execution, or broader QA coverage during verification, invoke qa-expert.

If verification fails, return to implementation and fix the issue before concluding.

Step 6: Conclude

End with exactly one of these outcomes:

• passed
• failed
• skipped

When concluding, include:

• brief summary of what changed
• verification used
• result
• remaining risk if any

If the result is skipped, include the reason and the specific risk introduced by not verifying.

Failure Conditions

Stop and resolve the issue before implementation when:

• requirements are unclear
• acceptance criteria are missing
• no verification strategy is defined

Loop back and keep working when:

• tests fail unexpectedly
• the verification command fails
• manual verification does not satisfy acceptance criteria

Optional Artifacts

Use lightweight artifacts only when they help:

• proposal.md
• design.md
• tests.md
• explicit verify command

Do not require a fixed directory structure unless the surrounding project already has one.