ex_unit

ExUnit testing automation with pre-commit test validation

Installation

npx claude-plugins install @bradleygolden/elixir/ex_unit

Contents

Folders: hooks, scripts

Files: CHANGELOG.md, README.md

Documentation

ExUnit testing automation plugin that validates tests pass before git commits.

Overview

This plugin automatically runs ExUnit tests before git commits, preventing broken code from being committed. It uses mix test --stale to intelligently run only tests for modules that have changed, keeping validation fast and efficient.

Installation

/plugin marketplace add github:bradleygolden/claude-marketplace-elixir
/plugin install ex_unit@elixir

Features

Pre-commit Test Validation

When it runs: Before any git commit command

What it does: Runs mix test --stale to validate tests pass for changed modules

Behavior:

• ✅ Fast: Only runs tests for modules that changed (--stale flag)
• ✅ Blocking: Prevents commits if tests fail (via JSON permissionDecision: “deny”)
• ✅ Smart: Skips if not an Elixir project or no tests exist
• ✅ Informative: Shows test failures with truncated output (50 lines max)

Performance: Typically 5-30 seconds depending on number of changed modules

How It Works

The --stale Flag

The key to performance is ExUnit’s --stale flag, which only runs tests for modules that have been modified since the last test run. This means:

• First commit after changes: Tests run for affected modules only
• Subsequent commits without code changes: No tests run (already validated)
• Large test suites: Only relevant subset runs

Hook Details

Hook Type: PreToolUse (blocks before bash commands execute) Matcher: Filters for git commit commands only Timeout: 60 seconds Note: Skips if project has a precommit alias (defers to precommit plugin) Blocking Behavior:

• Hook always exits with 0 (success)
• Blocking decision communicated via JSON output with permissionDecision: "deny"
• When tests fail: Outputs JSON with permissionDecision: “deny” and test failure details
• When tests pass: Outputs JSON with suppressOutput: true

Usage

Once installed, the plugin works automatically:

# Make changes to your code
$ edit lib/accounts.ex
$ edit test/accounts_test.exs

# Try to commit
$ claude
> commit these changes

# Plugin runs automatically
Running stale tests for changed modules...

# If tests pass:
✓ Tests passed
[Commit proceeds]

# If tests fail:
✗ 1 test failed

1) test creates user (MyApp.AccountsTest)
   test/accounts_test.exs:12
   Expected: {:ok, %User{}}
   Got: {:error, :invalid}

⚠️ Commit blocked. Fix failing tests before committing.

Configuration

No configuration needed! The plugin:

• Auto-detects Mix projects (looks for mix.exs)
• Auto-detects test directory (looks for test/)
• Uses sensible defaults for all options

When Tests Run

The plugin runs tests only when:

1. Command is a git commit (not status, add, etc.)
2. Current directory is part of a Mix project
3. Project has a test/ directory

It skips for:

• Non-Elixir projects
• Projects without tests
• Git commands other than commit
• Non-git bash commands

Performance Tips

The --stale flag makes this fast, but you can optimize further:

1. Run Full Suite Manually

# Before committing, run full suite yourself
$ mix test

# Then commit - stale detection means nothing runs again
$ git commit -m "message"

2. Keep Tests Fast

• Use async: true in test modules when possible
• Mock external dependencies
• Use setup blocks efficiently

3. Commit Frequently

Since only changed tests run, frequent commits keep validation fast

Troubleshooting

“Tests timed out”

If tests exceed 60 seconds, they’ll timeout. This usually means:

• Test suite is very large (even with --stale)
• Tests are slow (network calls, etc.)
• Many modules changed at once

Solution: Run mix test --stale manually to see which tests are slow

“No tests run but commit blocked”

This shouldn’t happen, but if it does:

• Check for compilation errors: mix compile
• Verify test files exist: ls test/
• Run tests manually: mix test --stale

“Want to skip tests for this commit”

The plugin blocks commits with failing tests intentionally. Options:

1. Fix the failing tests (recommended)
2. Temporarily disable plugin: /plugin uninstall ex_unit@elixir
3. Use --no-verify flag: Not recommended, bypasses all hooks

Examples

Example 1: Single Module Change

# Edit one file
$ edit lib/accounts.ex

# Only accounts_test.exs runs (2-5 seconds)
$ git commit -m "update accounts"
Running stale tests...
1 test file, 5 tests, 0 failures
✓ Tests passed

Example 2: Multiple Module Changes

# Edit several files
$ edit lib/accounts.ex lib/users.ex lib/posts.ex

# Three test files run (10-20 seconds)
$ git commit -m "update multiple modules"
Running stale tests...
3 test files, 24 tests, 0 failures
✓ Tests passed

Example 3: Test Failure

# Break a test
$ edit test/accounts_test.exs

$ git commit -m "broken test"
Running stale tests...

1) test creates user (AccountsTest)
  

...(truncated)

## Source

[View on GitHub](https://github.com/bradleygolden/claude-marketplace-elixir)