Generate RSpec Tests for Ruby Code

Generates comprehensive, maintainable RSpec test suites for Ruby applications - Rails models, controllers, service objects, and plain Ruby classes - following RSpec conventions and testing best practices.

Use this skill when writing new RSpec tests for a Rails model, controller, or service object, structuring test organization with describe/context blocks, mocking external dependencies, or configuring spec_helper.rb for a project. Not a fit for non-Ruby test frameworks or for testing frameworks other than RSpec within Ruby (e.g. Minitest).

Core principles: follow the Arrange-Act-Assert pattern, use descriptive describe/context blocks for logical organization, prefer let/let! over instance variables for test data, use describe for classes/methods and context for different conditions, and start example descriptions with verbs ("returns", "raises", "updates").

Provides a full Rails model test example covering validations (shoulda-matchers style validate_presence_of, validate_uniqueness_of), associations (have_many/belong_to), scopes (testing an .active scope with let!-created fixtures), and instance method behavior across multiple contexts (e.g. #full_name with and without a last name present). Provides a Rails controller test example covering GET/POST actions, checking response success, assigned instance variables, record count changes, redirects, and template rendering across valid/invalid parameter contexts.

Provides a service object test example (UserRegistrationService) testing success and failure paths - user creation, welcome email dispatch verification, and structured success/failure result objects with error presence. Advanced techniques include mocking/stubbing patterns (stubbing an external API call's return value, verifying a method was called with specific arguments, stubbing Time.current for time-dependent code), RSpec shared examples (an "auditable model" shared example testing timestamp columns and touch behavior, included via it_behaves_like), and custom matchers (a be_a_valid_email matcher using a regex).

Configuration guidance provides a spec_helper.rb block enabling expectation chain descriptions, partial double verification, shared context metadata behavior, filter_run_when_matching :focus filtering, disabled monkey patching, doc formatter for single-file runs, and randomized test order with a seeded RNG. Performance and quality tips recommend using build over create when persistence isn't needed, before(:all) cautiously for expensive setup, aggregate_failures for multiple related expectations, database cleaning strategies for test isolation, travel_to instead of stubbing Time.now for time-based tests, and keeping unit tests fast and single-responsibility while reserving integration tests for critical workflows.

Built for RSpec within Rails (ActiveRecord models, controllers) and plain Ruby/service objects, referencing shoulda-matchers-style validation/association matchers and FactoryBot-style build/create/attributes_for helpers.

Ruby/Rails developers writing or maintaining RSpec test suites who need concrete model, controller, and service object test patterns plus mocking and configuration guidance rather than basic RSpec syntax alone.

allow(ExternalApiService).to receive(:fetch_data).and_return(mock_data)
expect(EmailService).to have_received(:send_notification).with(user.email)