majiayu000/claude-skill-registry-data/when-to-write-tests

When to write tests

Test observable behavior through the capability's interface. Follow codebase-design for the shared rules and examples. Prefer a few tests that cover real behavior over a test for every private helper.

Default

No new test.

Smoke the changed path (run the thing). That is verification.

Write a test only when

• The user asked for one, or
• A public observable contract is new, changed, or has a reproduced bug that existing tests do not cover (store API, HTTP route, migration backfill, public calculation).

Choose the smallest test that exercises that contract through its interface. For a store, use the real persistence path where practical. For a public pure function, assert its input/output behavior directly. Test failure, ordering, and cleanup when they are part of the contract; do not add a layer of tests for private helpers or assertions about internal calls.

Put it next to the source as <file>.test.ts, not in a separate test/ or tests/ directory. Only a test that spawns the real server or CLI, or spans packages, goes in the repo-root tests/.

Do not write a test for

• Comment / docs-only edits
• Internal helpers, encoders, or bind-list rewrites already covered by behavior tests
• "Every new function/method"
• Edges an advisory invented that are not the contract
• Refactors that keep the same public behavior (existing tests are the regression net)

Apply repository requirements

Current user instructions and repository requirements take precedence over this skill. Check existing coverage before adding tests; a required regression test should reproduce the observable bug, not freeze its current implementation. Do not invoke TDD merely because a helper was added or moved. A successful smoke check is useful verification, but does not replace a required automated test.

Fair example

Seed old inbound tables, apply the migration, list events, assert facts and metadata survived and the matches table is gone.

Unfair example

A test per helper or per comment rewrite. Asserting that saveInvoice called private insertRow rather than that the invoice was saved.