elixir-test-runner

A tool for running and diagnosing ExUnit tests, the automated tests used by Elixir projects.

In plain words
What is it for?
Use it to run all tests, a file, a line, a name pattern, or tagged tests; exclude slow or integration tests; and run tests with coverage or detailed output.
Why use it?
It makes it easier to run only the tests relevant to a change and inspect failures instead of rerunning or searching through the whole test suite.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/mkreyman/bmad-elixir/elixir-test-runner
Any agent
npx skills add mkreyman/bmad-elixir --skill elixir-test-runner
Clone the repo
git clone --depth 1 https://github.com/mkreyman/bmad-elixir

Made for: Claude Code, Codex.

Per session 36 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,964 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00036 $0.01964
Opus 5 $0.00018 $0.00982
Sonnet 5 $0.00007 $0.00393
Haiku 4.5 $0.00004 $0.00196

Measured 2d ago against content hash e6f3438fa258, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

elixir-test-runner scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

priv/skills/elixir-test-runner/SKILL.md · 411 lines

How it starts

The opening of the file, as written. The whole thing — 411 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Elixir Test Runner

This skill helps run ExUnit tests efficiently with proper filtering, debugging, and error analysis.

When to Use

  • Running full test suite
  • Testing specific files or tests
  • Debugging test failures
  • Running tests with coverage
  • Testing in different environments

Basic Test Execution

Run All Tests

mix test

Run Specific Test File

mix test test/my_app/accounts_test.exs

Run Specific Test by Line Number

mix test test/my_app/accounts_test.exs:42

Run Tests Matching Pattern

# Run all tests with "user" in the name
mix test --only user

Test Filtering

By Tag

# In test file
@tag :integration
test "complex integration test" do
  # ...
end
# Run only integration tests
mix test --only integration

# Exclude slow tests
mix test --exclude slow

# Run everything except integration
mix test --exclude integration

By Module Pattern

# Run all controller tests
mix test test/**/controllers/*_test.exs

# Run all LiveView tests
mix test test/**/*_live_test.exs

Umbrella App Filtering

# Run tests for specific app
mix test apps/my_app/test

# Run all umbrella tests
mix test --only apps

Debugging Options

With Trace (Detailed Output)

mix test --trace

Shows each test as it runs - useful for hanging tests.

With Verbose Failures

mix test --max-failures 1

Stops after first failure for faster debugging.

With Test Seed

# Tests run in random order by default
# To reproduce specific order:
mix test --seed 123456

# See seed in output:
# "Randomized with seed 123456"

With IEx for Debugging

# Add IEx.pry() in test code
mix test --trace

Test Output Control

Show Only Failures

mix test --failed

Reruns only previously failed tests.

Stale Tests

mix test --stale

Only runs tests for changed files.

With Coverage

mix test --cover

Generates coverage report in cover/ directory.

Read the full file on GitHub · 411 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 411 lines · 36 tokens per session scan A e6f3438fa258

Subscribe to this mod's changes

elixir-test-runner is a skill published in the GitHub repository mkreyman/bmad-elixir (10 stars, last pushed 10mo ago), licensed MIT. It adds 36 tokens to every session and 1,964 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.