/exunit-code-review

name: exunit-code-review
description: 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.

ExUnit Code Review

Quick Reference

| Issue Type | Reference | |------------|-----------| | Async tests, setup, describe, tags | [references/exunit-patterns.md](references/exunit-patterns.md) | | Behavior-based mocking, expectations | [references/mox-boundaries.md](references/mox-boundaries.md) | | Bypass, Swoosh, Oban testing | [references/test-adapters.md](references/test-adapters.md) | | What to mock vs real, Ecto sandbox | [references/integration-tests.md](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](../review-verification-protocol/SKILL.md) (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.