45ck api-contract-testability-checker
Purpose
Check whether public APIs expose clear inputs, outputs, errors, and state transitions that are straightforward to verify in tests.
Trigger this skill when
- The current artifact is difficult to test directly or reliably.
- You suspect hidden dependencies, side effects, non-determinism, or awkward setup are harming test quality.
- You want design changes that improve testability before adding more tests.
Expected inputs
- API signatures
- docs/spec
- error model
- state model
Deliverables
- contract clarity findings
- verification gaps
- assertion strategy
- API improvement suggestions
Operating procedure
- Read the code or design with a testability lens rather than a feature lens.
- Identify collaborators, side effects, state transitions, environment assumptions, and setup cost.
- Separate core logic from orchestration, effects, and framework concerns.
- Surface the concrete causes of poor testability, not just the symptoms.
- Recommend low-risk refactors or abstractions that improve controllability and observability.
- Prioritize changes that reduce flakiness, setup burden, and mocking complexity.
Quality gates
- Findings are specific to the artifact, not generic testing advice.
- Recommendations reduce coupling or non-determinism in a concrete way.
- Hidden I/O, time, randomness, or state dependencies are called out when present.
- Output separates findings, refactor options, tradeoffs, and next actions.
Handoff targets
- testability-reviewer
- side-effect-isolation-reviewer
- determinism-reviewer
Output style
- Be explicit about uncertainty.
- Prefer concrete examples over abstract advice.
- Separate facts, risks, refactor options, and recommended next step.
- Flag where a simpler design change beats a heavier testing workaround.
Failure modes to avoid
- Do not prescribe mocks as the first answer to every problem.
- Do not hide framework coupling or hidden I/O behind euphemistic wording.
- Do not recommend invasive redesign when a small seam or abstraction is enough.
- Do not confuse code coverage with testability.
Minimum output skeleton
## Summary
## Findings
## Structured outputs
## Risks
## Refactor options
## Recommended next skill