exunit-code-review
Reviews ExUnit test code for proper patterns, boundary mocking with Mox, and test adapter usage. Use when reviewing _test.exs files or test helper configurations.
Resources
1Install
npx skillscat add existential-birds/beagle/exunit-code-review Install via the SkillsCat registry.
This skill evaluates ExUnit test code to ensure adherence to best practices in test structure, boundary mocking with Mox, and test adapter usage. It addresses issues like improper mocking of internal code, inconsistent test setup, and incorrect use of test adapters. Developers should apply it when reviewing _test.exs files or test helpers to maintain test reliability and alignment with recommended patterns.
ExUnit Code Review
Quick Reference
| Issue Type | Reference |
|---|---|
| Async tests, setup, describe, tags | references/exunit-patterns.md |
| Behavior-based mocking, expectations | references/mox-boundaries.md |
| Bypass, Swoosh, Oban testing | references/test-adapters.md |
| What to mock vs real, Ecto sandbox | references/integration-tests.md |
Mock Boundary Philosophy
Mock at external boundaries:
- HTTP clients, external APIs, third-party services
- Slow resources: file system, email, job queues
- Non-deterministic: DateTime.utc_now(), :rand
DO NOT mock internal code:
- Contexts, schemas, GenServers
- Internal modules, PubSub
- Anything you wrote
Review Checklist
Test Structure
- Tests are
async: trueunless sharing database state - Describe-blocks group related tests
- Setup extracts common test data
- Tests have clear arrange/act/assert structure
Mocking
- Mox used for external boundaries (HTTP, APIs)
- Behaviors defined for mockable interfaces
- No mocking of internal modules
- verify_on_exit! in setup for strict mocking
Test Adapters
- Bypass for HTTP endpoint mocking
- Swoosh.TestAdapter for email testing
- Oban.Testing for background job assertions
Database
- Ecto.Adapters.SQL.Sandbox for isolation
- Async tests don't share database state
- Fixtures/factories used consistently
Valid Patterns (Do NOT Flag)
- Mock in unit test, real in integration - Different test levels have different needs
- Not mocking database in integration tests - Database is internal
- Simple inline test data - Not everything needs factories
- Testing private functions via public API - Correct approach
Context-Sensitive Rules
| Issue | Flag ONLY IF |
|---|---|
| Not async | Test actually needs shared state |
| Missing mock | External call exists AND no mock/bypass |
| Mock internal | Module being mocked is internal code |
Before Submitting Findings
Use the issue format: [FILE:LINE] ISSUE_TITLE for each finding.
Load and follow review-verification-protocol before reporting any issue.
Categories
Install
npx skillscat add existential-birds/beagle/exunit-code-review Install via the SkillsCat registry.