RSpec Testing Patterns

RSpec Testing Patterns

Test Type Decision Tree

What am I testing?
│
├─ Model validations/associations/scopes?
│   └─ Model Spec (spec/models/)
│       └─ Use shoulda-matchers
│
├─ Service object business logic?
│   └─ Service Spec (spec/services/)
│       └─ Test inputs, outputs, side effects
│
├─ API endpoint behavior?
│   └─ Request Spec (spec/requests/)
│       └─ Test HTTP responses, JSON structure
│
├─ Full user flow with browser?
│   └─ System Spec (spec/system/)
│       └─ Use Capybara + Selenium
│
├─ ViewComponent rendering?
│   └─ Component Spec (spec/components/)
│       └─ Use render_inline
│
├─ Background job?
│   └─ Job Spec (spec/jobs/)
│       └─ Test perform + enqueuing
│
└─ Controller logic? (rare)
    └─ Request Spec preferred

NEVER Do This

NEVER use create when build works:

# WRONG - unnecessary DB writes
it 'validates presence of email' do
  user = create(:user, email: nil)
  expect(user.valid?).to be false
end

# RIGHT - use build for validation tests
it 'validates presence of email' do
  user = build(:user, email: nil)
  expect(user.valid?).to be false
end

NEVER test implementation, test behavior:

# WRONG - testing implementation details
it 'calls private method' do
  expect(service).to receive(:calculate_total)
  service.call
end

# RIGHT - test observable behavior
it 'returns correct total' do
  result = service.call
  expect(result.total).to eq(100)
end

NEVER use mystery guests (undefined variables):

# WRONG - where does user come from?
it 'creates task for user' do
  task = TasksManager::CreateTask.call(user: user)
  expect(task.user).to eq(user)
end

# RIGHT - explicit setup with let
let(:user) { create(:user) }

it 'creates task for user' do
  task = TasksManager::CreateTask.call(user: user)
  expect(task.user).to eq(user)
end

NEVER skip testing edge cases:

# WRONG - only happy path
describe '.call' do
  it 'creates task' do
    expect { service.call }.to change(Task, :count).by(1)
  end
end

# RIGHT - cover failure cases too
describe '.call' do
  context 'with valid params' do
    it 'creates task' do
      expect { service.call }.to change(Task, :count).by(1)
    end
  end

  context 'with invalid params' do
    it 'raises error' do
      expect { service.call(nil) }.to raise_error(ArgumentError)
    end
  end

  context 'when external API fails' do
    before { stub_api_failure }

    it 'returns failure result' do
      expect(service.call).to be_failure
    end
  end
end

NEVER forget cleanup in before blocks:

# WRONG - state leaks between tests
before(:all) do
  @user = create(:user)
end

# RIGHT - use transactional fixtures or per-test setup
let(:user) { create(:user) }

Directory Structure

spec/
├── rails_helper.rb
├── spec_helper.rb
├── support/
│   ├── factory_bot.rb
│   ├── shared_contexts/
│   └── shared_examples/
├── factories/
├── models/
├── services/
├── requests/
├── system/
├── components/
└── jobs/

FactoryBot Quick Reference

# Traits
create(:task, :completed, :express)

# Override attributes
create(:task, status: 'cancelled')

# Transient attributes
create(:bundle, task_count: 10)

Shoulda Matchers Quick Reference

Associations

it { is_expected.to belong_to(:account) }
it { is_expected.to have_many(:tasks).dependent(:destroy) }
it { is_expected.to have_one(:profile) }

Validations

it { is_expected.to validate_presence_of(:email) }
it { is_expected.to validate_uniqueness_of(:email).case_insensitive }
it { is_expected.to validate_length_of(:password).is_at_least(8) }
it { is_expected.to validate_numericality_of(:amount).is_greater_than(0) }

Enums

it { is_expected.to define_enum_for(:status).with_values([:pending, :active]) }

Common Matchers

Request Spec Pattern

RSpec.describe "Api::V1::Tasks", type: :request do
  let(:user) { create(:user) }
  let(:headers) { auth_headers(user) }

  describe "POST /api/v1/tasks" do
    let(:params) { { task: { title: "New" } } }

    it "creates task" do
      expect {
        post api_v1_tasks_path, params: params, headers: headers
      }.to change(Task, :count).by(1)

      expect(response).to have_http_status(:created)
    end
  end

  def json_response
    JSON.parse(response.body)
  end
end

System Spec Pattern

RSpec.describe "Tasks", type: :system do
  before { driven_by(:selenium_chrome_headless) }

  let(:user) { create(:user) }

  before { sign_in(user) }

  it "creates task with Turbo" do
    visit tasks_path

    fill_in "Title", with: "New Task"
    click_button "Create"

    expect(page).to have_content("New Task")
    expect(page).to have_current_path(tasks_path) # No redirect
  end
end

Service Spec Pattern

RSpec.describe TasksManager::CreateTask do
  let(:account) { create(:account) }
  let(:params) { { title: "Test" } }

  describe '.call' do
    subject(:result) { described_class.call(account: account, params: params) }

    context 'with valid params' do
      it { is_expected.to be_success }
      it { expect(result.data).to be_a(Task) }
    end

    context 'with invalid params' do
      let(:params) { {} }

      it { is_expected.to be_failure }
      it { expect(result.error).to include("required") }
    end
  end
end

Testing Async Jobs

# Test enqueuing
expect { service.call }.to have_enqueued_job(NotifyJob).with(task.id)

# Test execution
described_class.perform_now(task.id)
expect(task.reload.notified?).to be true

# Test inline
perform_enqueued_jobs { service.call }
expect(Notification.count).to eq(1)

Mocking External APIs

before do
  stub_request(:post, "https://api.example.com/endpoint")
    .to_return(status: 200, body: { success: true }.to_json)
end

# Test timeout
stub_request(:post, url).to_timeout

# Test error
stub_request(:post, url).to_return(status: 500)

Configuration

# spec/rails_helper.rb
RSpec.configure do |config|
  config.include FactoryBot::Syntax::Methods
  config.use_transactional_fixtures = true
  config.infer_spec_type_from_file_location!
end

Shoulda::Matchers.configure do |config|
  config.integrate do |with|
    with.test_framework :rspec
    with.library :rails
  end
end

References

Detailed patterns and examples in references/:

• factories.md - FactoryBot patterns, traits, transients
• model-specs.md - Shoulda matchers, callbacks, scopes
• request-specs.md - API testing, pagination, rate limiting
• system-specs.md - Capybara, Turbo testing
• service-specs.md - Service object testing patterns
• shared-examples.md - Shared examples and contexts
• component-job-specs.md - ViewComponent and job testing
• helpers-mocking.md - Test helpers, WebMock, VCR