Tests that matter

Skill yakoshiq/skills/skills/tests-that-matter

Write or review tests that prove observable behavior, failure semantics, invariants, and boundary cases. Use when adding tests, fixing brittle or mock-heavy tests, reviewing test quality, or when coverage exists but confidence does not.From its SKILL.md

Install

npx -y skills add yakoshiq/skills --skill tests-that-matter

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21 days oldThe repository was created 21 days ago. New is not bad, but a brand new repository carrying a familiar-sounding name is the shape a typosquat arrives in, and there has been no time for anyone else to find a problem with it.
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SKILL.md

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Tests That Matter

Prove behavior a caller or operator can observe. Green is not confidence.

Match the repo's test runner and style. Do not invent a framework, coverage cult, or TDD ceremony.

Choose scope

Review: findings only - no rewrite. Weak asserts, mock theater, missing failures/boundaries, false regressions.
Write / fix: add or reshape tests. Touch production only for a real test seam, and say so.
New feature work: when you change invariants or failure paths, update or add the focused cases that prove them.

Prove

Public outcomes: return values, raised/returned errors, persisted state, and effects at real external boundaries.
Distinct failure modes as distinct cases (validation vs not-found vs infra vs partial success). If effect A commits and B fails, assert both the committed state and the failure.
Invariants and boundaries that can actually break (empty, zero, max, off-by-one, idempotency).
A regression that fails on the old defect. If it stays green on broken code, it is not a regression test.

Avoid

Private helpers, call order inside the unit, and literal structure of the implementation.
Mocks of implementation details inside the unit. Prefer in-memory fakes for owned stateful collaborators; mock only narrow external or nondeterministic edges (network, clock, disk, queue, payment gateway).
Asserts that only restate the mock setup (toHaveBeenCalledWith with no outcome check).
Five near-duplicate cases when one table or parameterized rule states the policy.
Broad snapshots or full-object equality when a few precise fields carry the meaning.
Flakes: real sleeps, uncontrolled clocks/randomness, test-order dependence, shared mutable fixtures across cases.

Discipline

Prefer fewer sharper tests over a pile of weak ones.
Name tests by the behavior or risk they guard, not by the method under test alone.
If a test can stay green while the bug returns, delete or rewrite it.
Meet repo coverage gates when they exist; optimize for confidence, not percentage.
Ship tests plus a brief note of what confidence they add - no essay.

What ships with it

Read from the repository

Just SKILL.md. No reference files, no scripts.