Testing Essentials

Canonical FP bar: docs/fcis-engineering-rules.md — Functional Core, Imperative Shell: pure domain modules; side effects at edges. Prefer testing pure core without Repo; use DataCase only for true persistence boundaries.

RULES — Follow these with no exceptions

1. Follow the project's existing test setup patterns — don't inline DataCase/ConnCase boilerplate that the project already abstracts away 2. Use async: true only when safe — avoid for DB contexts with shared rows, LiveView, Application.put_env, and external services 3. Define test data in fixtures (test/support/) — never build it inline across multiple tests 4. Use has_element?/2 and element/2 for LiveView assertions — not html =~ "text" for structure checks 5. Always test the unauthorized case for any protected resource 6. Never hardcode dates — use relative timestamps to prevent flaky tests

FCIS at this boundary

Prefer unit-testing pure core without the database. Use DataCase for true persistence; use plain ExUnit for pure modules.