Module: Shoulda::Matchers::Independent

Overview

This module provides matchers that are used to test behavior outside of Rails-specific classes.

Instance Method Summary collapse

Instance Method Details

#delegate_method(delegating_method) ⇒ DelegateMethodMatcher

The delegate_method matcher tests that an object forwards messages to other, internal objects by way of delegation.

In this example, we test that Courier forwards a call to #deliver onto its PostOffice instance:

require 'forwardable'

class Courier
  extend Forwardable

  attr_reader :post_office

  def_delegators :post_office, :deliver

  def initialize
    @post_office = PostOffice.new
  end
end

# RSpec
describe Courier do
  it { should delegate_method(:deliver).to(:post_office) }
end

# Minitest
class CourierTest < Minitest::Test
  should delegate_method(:deliver).to(:post_office)
end

You can also use delegate_method with Rails's delegate macro:

class Courier
  attr_reader :post_office
  delegate :deliver, to: :post_office

  def initialize
    @post_office = PostOffice.new
  end
end

describe Courier do
  it { should delegate_method(:deliver).to(:post_office) }
end

To employ some terminology, we would say that Courier's #deliver method is the delegating method, PostOffice is the delegate object, and PostOffice#deliver is the delegate method.

Qualifiers

as

Use as if the name of the delegate method is different from the name of the delegating method.

Here, Courier has a #deliver method, but instead of calling #deliver on the PostOffice, it calls #ship:

class Courier
  attr_reader :post_office

  def initialize
    @post_office = PostOffice.new
  end

  def deliver(package)
    post_office.ship(package)
  end
end

# RSpec
describe Courier do
  it { should delegate_method(:deliver).to(:post_office).as(:ship) }
end

# Minitest
class CourierTest < Minitest::Test
  should delegate_method(:deliver).to(:post_office).as(:ship)
end
with_prefix

Use with_prefix when using Rails's delegate helper along with the :prefix option.

class Page < ActiveRecord::Base
  belongs_to :site
  delegate :name, to: :site, prefix: true
  delegate :title, to: :site, prefix: :root
end

# RSpec
describe Page do
  it { should delegate_method(:name).to(:site).with_prefix }
  it { should delegate_method(:name).to(:site).with_prefix(true) }
  it { should delegate_method(:title).to(:site).with_prefix(:root) }
end

# Minitest
class PageTest < Minitest::Test
  should delegate_method(:name).to(:site).with_prefix
  should delegate_method(:name).to(:site).with_prefix(true)
  should delegate_method(:title).to(:site).with_prefix(:root)
end
with_arguments

Use with_arguments to assert that the delegate method is called with certain arguments. Note that this qualifier can only be used when the delegating method takes no arguments; it does not support delegating or delegate methods that take arbitrary arguments.

Here, when Courier#deliver_package calls PostOffice#deliver_package, it adds an options hash:

class Courier
  attr_reader :post_office

  def initialize
    @post_office = PostOffice.new
  end

  def deliver_package
    post_office.deliver_package(expedited: true)
  end
end

# RSpec
describe Courier do
  it do
    should delegate_method(:deliver_package).
      to(:post_office).
      with_arguments(expedited: true)
  end
end

# Minitest
class CourierTest < Minitest::Test
  should delegate_method(:deliver_package).
    to(:post_office).
    with_arguments(expedited: true)
end
allow_nil

Use allow_nil if the delegation accounts for the fact that your delegate object could be nil. (This is mostly intended as an analogue to the allow_nil option that Rails' delegate helper takes.)

class Account
  delegate :plan, to: :subscription, allow_nil: true
end

# RSpec
describe Account do
  it { should delegate_method(:plan).to(:subscription).allow_nil }
end

# Minitest
class PageTest < Minitest::Test
  should delegate_method(:plan).to(:subscription).allow_nil
end



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# File 'lib/shoulda/matchers/independent/delegate_method_matcher.rb', line 173

def delegate_method(delegating_method)
  DelegateMethodMatcher.new(delegating_method).in_context(self)
end