minitest

# Minitest for Rails Comprehensive guide to testing Rails applications with Minitest, the default Rails testing framework. ## Test Case Classes Rails provides specialized test case base classes: | Base Class | Purpose | Location | |------------|---------|----------| | `ActiveSupport::TestCase` | Model and unit tests | `test/models/` | | `ActionDispatch::IntegrationTest` | Multi-controller workflow tests | `test/integration/` | | `ActionDispatch::SystemTestCase` | Browser-based end-to-end tests | `test/system/` | | `ActionController::TestCase` | Functional controller tests | `test/controllers/` | | `ActionView::TestCase` | View and helper tests | `test/helpers/` | | `ActionMailer::TestCase` | Mailer tests | `test/mailers/` | | `ActiveJob::TestCase` | Background job tests | `test/jobs/` | ## Configuration ```ruby # test/test_helper.rb ENV["RAILS_ENV"] ||= "test" require_relative "../config/environment" require "rails/test_help" class ActiveSupport::TestCase # Run tests in parallel parallelize(workers: :number_of_processors) # Load fixtures fixtures :all # Add helper methods here end ``` ## Directory Structure ``` test/ ├── controllers/ # Functional controller tests ├── fixtures/ │ ├── files/ # Upload test files │ ├── users.yml │ └── articles.yml ├── helpers/ # View helper tests ├── integration/ # Multi-controller tests ├── jobs/ # ActiveJob tests ├── mailers/ # Email tests ├── models/ # Model unit tests ├── system/ # Browser tests (Capybara) ├── application_system_test_case.rb └── test_helper.rb ``` ## Model Tests ```ruby # test/models/article_test.rb require "test_helper" class ArticleTest < ActiveSupport::TestCase # Setup runs before each test setup do @article = articles(:published) end # Associations test "belongs to user" do assert_respond_to @article, :user assert_instance_of User, @article.user end test "has many comments" do assert_respond_to @article, :comments end # Validations test "is invalid without title" do article = Article.new(body: "Content", user: @user) assert_not article.valid? assert_includes article.errors[:title], "can't be blank" end test "is invalid with title over 255 characters" do article = Article.new(title: "a" * 256, body: "Content", user: @user) assert_not article.valid? end test "is valid with all attributes" do article = Article.new(title: "Test", body: "Content", user: @user) assert article.valid? end # Scopes test ".published returns only published articles" do assert_includes Article.published, articles(:published) assert_not_includes Article.published, articles(:draft) end test ".recent orders by created_at descending" do recent = Article.recent.first assert_equal articles(:published), recent end # Instance methods test "#publish! changes status to published" do article = articles(:draft) article.publish! assert_equal "published", article.status assert_not_nil article.published_at end test "#published? returns true for published articles" do assert articles(:published).published? assert_not articles(:draft).published? end end ``` ## Controller Tests (Functional) ```ruby # test/controllers/articles_controller_test.rb require "test_helper" class ArticlesControllerTest < ActionDispatch::IntegrationTest setup do @article = articles(:published) @user = users(:one) end test "should get index" do get articles_url assert_response :success end test "should get show" do get article_url(@article) assert_response :success end test "should get new" do get new_article_url assert_response :success end test "should create article" do assert_difference("Article.count") do post articles_url, params: { article: { title: "New Article", body: "Content" } } end assert_redirected_to article_url(Article.last) end test "should not create article with invalid params" do assert_no_difference("Article.count") do post articles_url, params: { article: { title: "" } } end assert_response :unprocessable_entity end test "should update article" do patch article_url(@article), params: { article: { title: "Updated Title" } } assert_redirected_to article_url(@article) @article.reload assert_equal "Updated Title", @article.title end test "should destroy article" do assert_difference("Article.count", -1) do delete article_url(@article) end assert_redirected_to articles_url end end ``` ## Integration Tests ```ruby # test/integration/user_flows_test.rb require "test_helper" class UserFlowsTest < ActionDispatch::IntegrationTest test "user can create article" do get new_article_url assert_response :success post articles_url, params: { article: { title: "My First Article", body: "Content" } } follow_redirect! assert_select "h1", "My First Article" end test "browsing articles as guest" do get articles_url assert_response :success assert_select "article", minimum: 1 get article_url(articles(:published)) assert_response :success assert_select "h1", articles(:published).title end end ``` ## System Tests ```ruby # test/application_system_test_case.rb require "test_helper" class ApplicationSystemTestCase < ActionDispatch::SystemTestCase driven_by :selenium, using: :headless_chrome, screen_size: [1400, 1400] end ``` ```ruby # test/system/articles_test.rb require "application_system_test_case" class ArticlesTest < ApplicationSystemTestCase setup do @article = articles(:published) end test "visiting the index" do visit articles_url assert_selector "h1", text: "Articles" end test "creating an article" do visit new_article_url fill_in "Title", with: "System Test Article" fill_in "Body", with: "This is test content." click_on "Create Article" assert_text "Article was successfully created" assert_text "System Test Article" end test "updating an article" do visit article_url(@article) click_on "Edit" fill_in "Title", with: "Updated Title" click_on "Update Article" assert_text "Article was successfully updated" assert_text "Updated Title" end test "destroying an article" do visit article_url(@article) click_on "Delete", match: :first assert_text "Article was successfully destroyed" end test "adding comment with Turbo" do visit article_url(@article) fill_in "comment_body", with: "Great article!" click_on "Add Comment" within "#comments" do assert_text "Great article!" end end end ``` ## Fixtures ```yaml # test/fixtures/users.yml one: email: user1@example.com name: Test User admin: email: admin@example.com name: Admin User role: admin # test/fixtures/articles.yml published: title: Published Article body: This is published content. status: published user: one published_at: <%= 1.day.ago %> created_at: <%= 2.days.ago %> draft: title: Draft Article body: This is draft content. status: draft user: one created_at: <%= 1.day.ago %> # With associations # test/fixtures/comments.yml one: body: Great article! article: published user: one ``` ## Assertions Reference ### Basic Assertions ```ruby assert value # truthy assert_not value # falsy (Rails) refute value # falsy (Minitest) assert_equal expected, actual # == assert_not_equal unexpected, actual assert_same expected, actual # same object assert_nil value assert_not_nil value assert_empty collection assert_not_empty collection assert_includes collection, item assert_not_includes collection, item assert_instance_of Class, object assert_kind_of Class, object assert_respond_to object, :method assert_match /regex/, string assert_no_match /regex/, string assert_raises(ErrorClass) { action } assert_nothing_raised { action } ``` ### Rails-Specific Assertions ```ruby # Count changes assert_difference "Article.count", 1 do post articles_url, params: { article: valid_params } end assert_no_difference "Article.count" do post articles_url, params: { article: invalid_params } end # Multiple counts assert_difference ["Article.count", "Tag.count"], 1 do post articles_url, params: params_with_tag end # HTTP responses assert_response :success # 200 assert_response :redirect # 3xx assert_response :not_found # 404 assert_response :unprocessable_entity # 422 assert_response 201 # Specific code # Redirects assert_redirected_to article_url(@article) assert_redirected_to root_url # Query count (prevent N+1) assert_queries_count(2) do Article.includes(:user).each { |a| a.user.name } end # Enqueued jobs assert_enqueued_jobs 1 do ArticleMailer.published(@article).deliver_later end assert_enqueued_with(job: NotifyJob, args: [@article]) do @article.publish! end # Enqueued emails assert_enqueued_emails 1 do UserMailer.welcome(@user).deliver_later end # DOM assertions (system tests) assert_selector "h1", text: "Title" assert_text "Expected content" assert_no_text "Should not appear" assert_select "article", count: 3 ``` ## Mailer Tests ```ruby # test/mailers/user_mailer_test.rb require "test_helper" class UserMailerTest < ActionMailer::TestCase test "welcome email" do user = users(:one) email = UserMailer.welcome(user) assert_emails 1 do email.deliver_now end assert_equal ["welcome@example.com"], email.from assert_equal [user.email], email.to assert_equal "Welcome to Our App", email.subject assert_match "Hello #{user.name}", email.body.encoded end test "welcome email is enqueued" do user = users(:one) assert_enqueued_emails 1 do UserMailer.welcome(user).deliver_later end end end ``` ## Job Tests ```ruby # test/jobs/article_notification_job_test.rb require "test_helper" class ArticleNotificationJobTest < ActiveJob::TestCase test "sends notification to subscribers" do article = articles(:published) assert_enqueued_emails article.subscribers.count do ArticleNotificationJob.perform_now(article) end end test "job is enqueued on publish" do article = articles(:draft) assert_enqueued_with(job: ArticleNotificationJob, args: [article]) do article.publish! end end test "performs enqueued jobs" do article = articles(:draft) article.publish! perform_enqueued_jobs # Verify side effects assert_emails article.subscribers.count end end ``` ## Helper Tests ```ruby # test/helpers/articles_helper_test.rb require "test_helper" class ArticlesHelperTest < ActionView::TestCase test "format_status returns badge HTML" do result = format_status("published") assert_dom_equal '<span class="badge badge-success">Published</span>', result end test "reading_time calculates minutes" do article = articles(:published) article.body = "word " * 500 # 500 words assert_equal "2 min read", reading_time(article) end end ``` ## Parallel Testing ```ruby # test/test_helper.rb class ActiveSupport::TestCase # Run tests in parallel with specified workers parallelize(workers: :number_of_processors) # Or with specific count parallelize(workers: 4) # Setup for parallel testing parallelize_setup do |worker| # Setup for each worker end parallelize_teardown do |worker| # Cleanup for each worker end end ``` ## Running Tests ```bash # All tests rails test # Specific directory rails test test/models # Single file rails test test/models/article_test.rb # Single test by line number rails test test/models/article_test.rb:25 # Single test by name rails test test/models/article_test.rb -n test_is_invalid_without_title # System tests only rails test:system # All including system rails test:all # Parallel execution rails test:parallel:all # With verbose output rails test -v # Stop on first failure rails test -f # Specific seed (for reproducibility) rails test --seed 12345 ``` ## Additional Resources ### Reference Files - **`references/minitest-patterns.md`** - Advanced patterns, custom assertions, test organization