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).