mixology_hook.rb

require "rubygems"
gem "mixology", "0.2.0"
require "mixology"

Mixology.class_eval do
  def mixin_with_hook(mod)
    result = mixin_without_hook(mod)
    if mod.respond_to?(:mixed_into)
      mod.mixed_into(self)
    end
    result
  end
  alias_method :mixin_without_hook, :mixin
  alias_method :mixin, :mixin_with_hook

  def unmix_with_hook(mod)
    result = unmix_without_hook(mod)
    if mod.respond_to?(:unmixed_from)
      mod.unmixed_from(self)
    end
    result
  end
  alias_method :unmix_without_hook, :unmix
  alias_method :unmix, :unmix_with_hook
end

require "test/unit"

class MixologyHookTest < Test::Unit::TestCase
  def self.test(description, &block)
    define_method "test_#{description}", &block
  end

  test "mixin calls the mixed_into hook if it's defined" do
    module_with_hook = Module.new do
      class << self
        attr_reader :object_passed_to_hook
      end

      def self.mixed_into(object)
        @object_passed_to_hook = object
      end
    end
    o = Object.new
    o.mixin module_with_hook
    assert_equal o, module_with_hook.object_passed_to_hook
  end

  test "mixin doesn't call hook if it's not defined" do
    assert_nothing_raised do
      o = Object.new
      o.mixin Module.new
    end
  end

  test "mixin returns same value regardless of whether it called the hook or not" do
    module_with_hook = Module.new do
      def self.mixed_into(object)
        @hook_called = true
      end

      def self.hook_called?
        @hook_called
      end
    end
    module_without_hook = Module.new
    o = Object.new
    return_value_without_hook = o.mixin(module_without_hook)
    return_value_with_hook = o.mixin(module_with_hook)
    assert_equal return_value_with_hook, return_value_without_hook
  end

  test "unmix calls the unmixed_from hook if it's defined" do
    module_with_hook = Module.new do
      class << self
        attr_reader :object_passed_to_hook
      end

      def self.unmixed_from(object)
        @object_passed_to_hook = object
      end
    end
    o = Object.new
    o.mixin module_with_hook
    o.unmix module_with_hook
    assert_equal o, module_with_hook.object_passed_to_hook
  end

  test "unmixin doesn't call hook if it's not defined" do
    assert_nothing_raised do
      o = Object.new
      mod = Module.new
      o.mixin mod
      o.unmix mod
    end
  end

  test "unmix returns same value regardless of whether it called the hook or not" do
    module_with_hook = Module.new do
      def self.mixed_into(object)
        @hook_called = true
      end

      def self.hook_called?
        @hook_called
      end
    end
    module_without_hook = Module.new
    o = Object.new
    o.mixin(module_without_hook)
    return_value_without_hook = o.unmix(module_without_hook)
    o.mixin(module_with_hook)
    return_value_with_hook = o.unmix(module_with_hook)
    assert_equal return_value_with_hook, return_value_without_hook
  end
end