Testing Rails apps

Rails' built-in testing stack lets you change code confidently, and every generator creates test stubs for you.

Rails uses Minitest with Rails-specific helpers. Run everything with bin/rails test, a file with bin/rails test test/models/article_test.rb, or one test by line: ...article_test.rb:12. Tests run in parallel and in random order, each inside a transaction that's rolled back.

Kinds of tests:

Model tests (ActiveSupport::TestCase): validations, scopes and business methods.
Integration tests (ActionDispatch::IntegrationTest): real HTTP requests through routes, middleware and controllers: get articles_url, post articles_url, params: {...}, then assert_response :success, assert_redirected_to, assert_select "h1", "Articles".
System tests (ApplicationSystemTestCase): drive a real browser through Capybara (visit, fill_in, click_on, assert_text). Slowest, so keep them for critical journeys.
Job and mailer tests: assert_enqueued_with(job: ...), perform_enqueued_jobs, assert_emails 1.

Fixtures in test/fixtures/*.yml load named sample records before the suite: articles(:published) returns one. They are fast and referenced by name, and associations can point to other fixtures by label. Many teams use factory_bot instead.

Useful helpers: assert_difference("Article.count", 1) { ... }, assert_changes, travel_to(Time.zone.local(2025, 1, 1)), and sign_in_as(user) helpers for authenticated tests.

RSpec (rspec-rails) is a popular alternative with the same concepts and a different syntax.

Example

# test/fixtures/articles.yml
# published:
#   title: Hello
#   slug: hello
#   published: true
#   author: ada          # references users(:ada)

# test/integration/articles_flow_test.rb
require "test_helper"

class ArticlesFlowTest < ActionDispatch::IntegrationTest
  setup { sign_in_as users(:ada) }     # your test helper that signs in
  test "creates an article" do
    assert_difference("Article.count", 1) do
      post articles_url, params: { article: { title: "New", body: "Text" } }
    end
    assert_redirected_to article_url(Article.last)
    follow_redirect!
    assert_select "h1", "New"
  end
  test "rejects a blank title" do
    post articles_url, params: { article: { title: "" } }
    assert_response :unprocessable_entity
  end
end

Remember

bin/rails test runs Minitest in parallel with transactional isolation
Integration tests cover routes to views; system tests drive a real browser
Fixtures provide named sample records; assert_difference checks side effects

Watch out for

Writing mostly slow system tests for logic that model or integration tests could cover faster.

Check yourself

Which test type exercises routing, controllers and views through HTTP without a browser?

Official docs: guides.rubyonrails.org/testing.html

Example

Remember

Watch out for

Check yourself

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