exunit-testing

name: exunit-testing description: Adding or fixing ExUnit tests (unit, ConnCase, DataCase, LiveView). Use when writing tests, fixing failing tests, or improving test structure and coverage. user-invocable: false

ExUnit Testing

When to Use

• Adding tests for contexts, controllers, LiveView, or other modules (unit or integration).
• Fixing failing tests (determine whether the failure is in implementation or test; fix minimally).
• Improving test structure (describe, setup, tags) or readability.

Principles

1. Layout: Mirror source layout: test/my_app/user_test.exs for lib/my_app/user.ex; test/my_app_web/live/dashboard_live_test.exs for LiveView. Use describe and test "description" with clear descriptions.
2. ConnCase: For HTTP; use get, post, etc. and assert on response and assigns. Set up auth/session in setup when needed.
3. DataCase: For repo and context tests; use Repo and context functions. Use setup for fixtures; prefer factories or explicit inserts.
4. LiveView tests: Use Phoenix.LiveViewTest (render, follow_redirect, element, etc.). Test mount, handle_params, and key handle_events; assert on rendered content and navigation.
5. Assertions: Prefer assert, assert_raise, refute. Use pattern matching in assertions when the shape is important (assert {:ok, x} = ...). Keep expected values explicit.
6. Setup: Use setup or setup_all for shared context; use @tag for expensive or integration tests; run with mix test --only tag when needed.
7. Verification: Run mix test (optionally with path or filter) to verify. Do not change behaviour beyond what is needed to fix the failure.