Minitest Testing

Minitest Testing for Rails

Write comprehensive, maintainable Minitest tests following Rails conventions and best practices. This skill provides patterns for model tests, controller tests, system tests with Capybara, and fixture usage.

• Writing new tests for models, controllers, or system workflows
• Reviewing existing test coverage and improving quality
• Fixing failing tests or debugging test issues
• Setting up test fixtures and test helpers
• Writing system tests for end-to-end user workflows
• Testing Hotwire/Turbo behavior in system tests

• Built-in Framework - No additional gems needed, part of Rails
• Fast Execution - Lightweight and performant test suite
• Rails Integration - First-class support in Rails framework
• Fixture Support - Simple YAML-based test data
• System Tests - Built-in Capybara integration for browser testing
• Parallel Testing - Run tests in parallel with bin/rails test:parallel

Before completing testing work:

• ✅ Tests follow Minitest naming convention: test "descriptive name"
• ✅ Fixtures used appropriately for test data
• ✅ System tests cover critical user workflows
• ✅ Assertions are specific and descriptive
• ✅ Tests are independent and can run in any order
• ✅ All tests passing: bin/rails test

• Use descriptive test names: test "creates post with valid attributes"
• One assertion concept per test (may use multiple assert calls)
• Use specific assertions: assert_equal, assert_redirected_to, not just assert
• Reference fixtures with symbols: posts(:published_post)
• Use setup and teardown for test lifecycle management
• Use assert_difference for counting changes
• System tests for critical workflows, controller/model tests for details
• Run tests before committing code

---

Core Testing Principles

1. Test Structure

Organize tests with clear phases:

test "creates article with valid attributes" do
  # Arrange - set up test data
  user = users(:alice)

  # Act - perform the action
  article = Article.create(
    title: "Test Article",
    body: "Content here",
    user: user
  )

  # Assert - verify the outcome
  assert article.persisted?
  assert_equal "Test Article", article.title
end

2. Test Independence

Each test should be independent and able to run in any order. Use setup for common initialization:

class ArticleTest 

draft:
  user: bob
  title: Draft Article
  body: Work in progress
  status: draft

Using Fixtures in Tests

test "finds published articles" do
  published = articles(:published)
  draft = articles(:draft)

  results = Article.published

  assert_includes results, published
  assert_not_includes results, draft
end

---

Test Helpers

Authentication Helper

# test/test_helper.rb
class ActionDispatch::IntegrationTest
  def sign_in_as(user)
    post login_path, params: { email: user.email, password: "password" }
  end
end

Custom Assertions

# test/test_helper.rb
module ActiveSupport
  class TestCase
    def assert_valid(record)
      assert record.valid?, "Expected #{record.class} to be valid, errors: #{record.errors.full_messages}"
    end
  end
end

---

Running Tests

# Run all tests
bin/rails test

# Run specific test file
bin/rails test test/models/article_test.rb

# Run specific test by line number
bin/rails test test/models/article_test.rb:12

# Run tests by pattern
bin/rails test test/models/*_test.rb

# Run system tests only
bin/rails test:system

# Run tests in parallel
bin/rails test:parallel

# Run with verbose output
bin/rails test -v

# Run and show coverage
COVERAGE=true bin/rails test

---

• rails-models - ActiveRecord patterns for database models
• rails-controllers - Controller patterns and RESTful design
• rails-hotwire - Testing Turbo Frames/Streams and Stimulus
• rails-jobs - Testing background jobs with SolidQueue
• rails-mailers - Testing email delivery with ActionMailer

Official Documentation:

• Rails Testing Guide - Comprehensive Rails testing guide
• Minitest Documentation - Minitest framework docs
• Capybara Cheat Sheet - System test selectors

Tools:

• SimpleCov - Code coverage for Ruby
• shoulda-matchers - Additional matchers for Rails

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: Shoebtamboli
• Source: Shoebtamboli/railsclaude_skills
• License: MIT
• Homepage: https://rubygems.org/gems/railsclaudeskills

Install and usage instructions live in the source repository linked above.