ammeter

A gem that allows for you to write specs for your Rails 3 generators

alexrothenberg

Ruby

Ammeter

A gem that makes it easy to write specs for your Rails 3 Generators.

RSpec is using ammeter to
spec
its
own
generators
and we think you may find it useful too.

An ammeter is used to measure electrical current and
electricity can be produced by a generator.

Installation

Add this line to your Gemfile (or gemspec):

gem 'ammeter'

And then execute:

$ bundle

Add:

require 'ammeter/init'

To your spec/spec_helper.rb.

Example

require 'spec_helper'

# Generators are not automatically loaded by Rails
require 'generators/rspec/model/model_generator'

describe Rspec::Generators::ModelGenerator, :type => :generator do
  # Tell the generator where to put its output (what it thinks of as Rails.root)
  destination File.expand_path("../../../../../tmp", __FILE__)
  before do
    prepare_destination
  end

  # using mocks to ensure proper methods are called
  # invoke_all - will call all the tasks in the generator
  it 'should run all tasks in the generator' do
    gen = generator %w(posts)
    gen.should_receive :create_model_spec
    gen.should_receive :create_fixture_file
    capture(:stdout) { gen.invoke_all }
  end

  # invoke_task - will call just the named task in the generator
  it 'should run a specific tasks in the generator' do
    gen = generator %w(posts)
    gen.should_receive     :create_model_spec
    gen.should_not_receive :create_fixture_file
    capture(:stdout) { gen.invoke_task :create_model_spec }
  end

  # custom matchers make it easy to verify what the generator creates
  describe 'the generated files' do
    before do
      run_generator %w(posts)
    end
    describe 'the spec' do
      # file - gives you the absolute path where the generator will create the file
      subject { file('spec/models/posts_spec.rb') }

      # is_expected_to contain - verifies the file's contents
      it { is_expected_to contain /require 'spec_helper'/ }
      it { is_expected_to contain /describe Posts/ }
    end
    describe 'the migration' do
      subject { migration_file('db/migrate/create_posts.rb') }

      # is_expected_to be_a_migration - verifies the file exists with a migration timestamp as part of the filename
      it { is_expected_to be_a_migration }
      it { is_expected_to contain /create_table/ }
    end
  end
end

Available matchers

contain - verifies the file’s contents
be_a_migration - verifies the file exists with a migration timestamp as part of the filename
have_method - verifies the file (or a class withing it) implements a method
have_correct_syntax - verifies the file has correct syntax and is not broken (works for .rb, .erb and .haml files)

Contributing