Coverage Policy

Canonical source: testing/coverage-policy.md — this page is rendered from it on every publish; edit the source.

Coverage Policy

Coverage is proportional to blast radius. High enough everywhere to prove edge cases were considered; exhaustive on the pure logic where a wrong branch is catastrophic.

Targets

The enforced numbers — declared thresholds, the floors CI enforces, the changed-lines target and the dated path to 92 % — live in one place: rules/22 rule 2, backed by tools/coverage/thresholds.json. This page does not restate them.

Scope	statements	lines	functions	branches
Pure critical logic (see list)	100%	100%	100%	100% branch

Pure critical logic (no I/O, high blast radius) — must reach 100% branch:

• Zod schemas / DTO validators
• Mappers (BE↔wire, entity↔DTO, event payload builders)
• Permission / ownership decision functions
• Query-key builders (frontend TanStack Query keys)
• Event-payload validators (RabbitMQ consumers)

These are cheap to test exhaustively and expensive to get wrong (an untested branch here is a data leak, a broken cache, or a swallowed event). See ../memory/testing-strategy.md.

Enforcement

• CI runs every workspace suite with --coverage and the workspace's floor (rules/22 rule 2); a metric below it fails the build, and the lines a pull request changes must meet changedLines on their own.
• Pure-critical modules that must hit 100% branch carry their own stricter per-path entry under vitest coverage.thresholds (a glob key) so a regression there fails.
• Coverage is ratcheted, never lowered. If a change drops a folder below its threshold, fix the test gap before merging — never edit the threshold down to land the change (../memory/testing-strategy.md).

Coverage is a proxy, not the goal

High coverage of trivial glue is not quality; it can hide untested risk. The number is a proxy for "did you think about the edge cases?" — pair it with risk-based design (testing-strategy) and reject the fixed-count-quota anti-pattern. Skip only trivial getters/setters and framework boilerplate.

Banned coverage-gaming

• Lowering a vitest coverage.thresholds value, a floor or changedLines to land a change.
• .toBeDefined()-only assertions to inflate line coverage without asserting behavior.
• xit / .skip to dodge a failing-but-real test.
• Excluding a real logic file from coverage collection to hide a gap.

Reporting

Coverage is reported per workspace by the CI test job (and coverage-merge for a sharded suite); npm run coverage:measure reports it locally (quality-gates). New code in a change should not drop the workspace's existing coverage.

Related

• Quality gates · Unit testing · ADR-063 coverage-targets · ../memory/testing-strategy.md