igmarin/rails-agent-skills

Curated library of 28 atomic skills and 9 personas for Ruby on Rails development. Organized by category: testing, code-quality, engines, infrastructure, api, context, and personas. Covers code review, architecture, security, testing (RSpec), engines, Hotwire, and TDD automation. Shared Ruby skills (YARD docs, DDD, service objects) have moved to ruby-core-skills.

1.16x

Quality

95%

Does it follow best practices?

Impact

93%

1.16x

Average score across 28 eval scenarios

Securityby

Advisory

Suggest reviewing before use

name:: test-engine
type:: atomic
license:: MIT
description:: Use when writing and configuring RSpec tests for Rails engines — must ensure that a dummy app exists for testing, add the smallest integration test that proves mounting and boot and verify it passes before continuing, and run the full test suite via bundle exec rspec to verify all specs pass. Key capabilities: request and routing specs with namespace scoping, generator idempotency, configuration testing.
metadata:: {"version":"1.0.0","user-invocable":"true"}

Test Engine

Name: igmarin/rails-agent-skills
Rating: 93.27 (1 reviews)
Author: igmarin

HARD-GATE

EVERY engine MUST have a dummy app for testing.
If it doesn't exist, generate it:
cd my_engine && bundle exec rails plugin new . --dummy-path=spec/dummy --skip-git

Validate the dummy app boots before proceeding:
cd spec/dummy && bundle exec rails runner "puts 'Boot OK'"

If this fails, check the engine's `engine.rb` initializer order and ensure the engine is correctly mounted in `spec/dummy/config/routes.rb` before writing any specs.

Core Process

Identify the engine type and public behaviors.
Add the smallest integration test that proves mounting and boot work. Verify it passes before continuing — if it fails, check engine.rb initializer order and mount configuration.
Add request, routing, configuration, and generator coverage as needed.
Add regression tests for coupling bugs before refactoring.
Run the full test suite (bundle exec rspec) to verify all specs pass.

Minimal request spec to prove the engine mounts:

# spec/requests/my_engine/root_spec.rb
require 'rails_helper'

RSpec.describe 'MyEngine mount', type: :request do
  it 'returns ok for the engine root' do
    get my_engine.root_path
    expect(response).to have_http_status(:ok)
  end
end

Configuration spec (engine respects host config):

# spec/my_engine/configuration_spec.rb
RSpec.describe MyEngine::Configuration do
  around do |example|
    original = MyEngine.config.widget_count
    MyEngine.config.widget_count = 3
    example.run
    MyEngine.config.widget_count = original
  end

  it 'uses configured value' do
    expect(MyEngine.config.widget_count).to eq(3)
  end
end

Advanced Coverage Patterns

Namespace-scoped routing spec:

# spec/routing/my_engine/widgets_routing_spec.rb
require 'rails_helper'

RSpec.describe MyEngine::WidgetsController, type: :routing do
  routes { MyEngine::Engine.routes }

  it 'routes GET /widgets to widgets#index' do
    expect(get: '/widgets').to route_to('my_engine/widgets#index')
  end
end

Generator idempotency spec:

# spec/generators/my_engine/install_generator_spec.rb
require 'rails_helper'
require 'generators/my_engine/install/install_generator'

RSpec.describe MyEngine::Generators::InstallGenerator, type: :generator do
  destination File.expand_path('../tmp', __dir__)

  before { prepare_destination }

  it 'generates the initializer' do
    run_generator
    expect(file('config/initializers/my_engine.rb')).to exist
  end

  it 'is idempotent on re-run' do
    run_generator
    expect { run_generator }.not_to raise_error
    expect(file('config/initializers/my_engine.rb')).to exist
  end
end

Output Style

When completing engine test setup, summarise results as:

Engine Test Report — [Engine Name]
- Dummy app: [location], boot ✓, migrations ✓
- Specs: mounting ✓, generators ✓, core (<n> examples, 0 failures)
- Suite: bundle exec rspec — <n> examples, 0 failures

Integration

Skill	When to chain
create-engine	When structuring the engine for testability or adding configuration seams
review-engine	When validating test coverage adequacy or identifying gaps
write-tests	When improving spec structure, matchers, or shared examples

.tessl-plugin

evals

skills

api

context

infrastructure

personas

testing

README.md

tile.json