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.

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: true unless 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

Gates (sequence)

Complete in order. Do not emit a finding until the prior step passes for that issue.

1. Evidence from the file — Open the test module (or helper) and tie the claim to concrete lines.

   • Pass when: Each prospective finding includes [FILE:LINE] and a one-line factual description of what is on that line (or an adjacent line you name), not a generic style complaint.

2. ExUnit false-positive veto — Check this skill’s Valid Patterns and Context-Sensitive Rules for the case.

   • Pass when: You can state “not covered by Do NOT Flag / Flag ONLY IF” in one sentence, or you drop the finding.

3. Cross-protocol verification — Apply review-verification-protocol (e.g. read full function/block, search usages before “unused” claims) to that same finding.

   • Pass when: At least one protocol check relevant to the claim type is satisfied and would appear in your rationale if challenged.

Before Submitting Findings

Use [FILE:LINE] ISSUE_TITLE per finding after Gates (sequence) and the linked protocol are satisfied.