coding-unit-test

Files (2)

• README.md
• SKILL.md

SKILL.md (first lines)

Discipline for useful, deterministic tests. No unnecessary tooling. No internal coupling.

## Outcome

Prove stable behavior. Follow repo idiom. Never bind to implementation internals.

## Inspect First

Before writing tests:

- test command and framework in use.
- test locations and file naming convention.
- fixtures, fakes, mocks, helpers in use.
- assertion idiom and async/error handling.
- nearby tests for the same boundary.

Existing setup: do NOT add framework, runner, layout, or assertion library unless it genuinely cannot test the contract.

No setup exists:

- material, repo-wide framework choice: ask.
- clear ecosystem default: choose it, state choice.
- no clear default: choose one sane default, state choice; use root `tests/` unless language or tooling convention gives stronger evidence.

## Design

1. Name stable module boundary.
2. State contract: inputs, outputs, effects, invariants, failures.
3. Choose honest test level:
   - pure unit.
   - unit with fake at adapter seam.
   - integration test.
   - boundary too muddy: improve design before forcing test.
4. Cover behavior branches, errors, and regressions with focused named cases.
5. Assert observable results only. Private calls, internal structure, incidental order: untested.

Prefer: pure functions, explicit dependencies, adapter-isolated effects, deterministic time/randomness, narrow fakes.

Painful setup signals bad boundary. Improve boundary before adding mock scaffolding.

Reject:

- booting half system for local logic.
- mocks that restate implementation or lack contract.
- timing/network/filesystem/randomness/shared-state flake sources.
- snapshots/goldens where explicit assertions say more.

## TDD and Coverage

- Stable, valuable seam: test before, with, or after change — favor early feedback.
- Tiny glue, exploratory code, unstable interface: no ritual test-first.
- Coverage measures gaps; never chase percentage with low-value tests.
- Intentional contract change: update affected tests — do not preserve obsolete expectations.

## Validate

Run narrow relevant tests first, then repo-standard test command when proportionate. Report exact command, result, and unrun scope. Report coverage metric only from coverage command; inspection may identify untested paths.

## Escalate

Ask before:

- competing framework conventions within the same repo.
- large testability refactor.
- unclear or conflicting test policy.

## Boundaries

- Stable behavior deserves tests; every glue line does not.
- Integration behavior stays labelled integration.
- Repo forbids or limits tests: obey.
- Not for test infrastructure or CI configuration.

From andresgongora/agent-config, MIT.

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