Add spec for Equalizer#included

lib/equalizer.rb

@@ -30,6 +30,7 @@ def initialize(*keys)
   #
   # @api private
   def included(descendant)
+    super
     descendant.module_eval { include Methods }
   end
 

spec/unit/equalizer/included_spec.rb

@@ -0,0 +1,40 @@
+# encoding: utf-8
+
+require 'spec_helper'
+
+describe Equalizer, '#included' do
+  subject { descendant.instance_exec(object) { |mod| include mod } }
+
+  let(:object)     { described_class.new        }
+  let(:descendant) { Class.new                  }
+  let(:superclass) { described_class.superclass }
+
+  before do
+    # Prevent Module.included from being called through inheritance
+    described_class::Methods.stub(:included)
+  end
+
+  around do |example|
+    # Restore included method after each example
+    superclass.class_eval do
+      alias_method :original_included, :included
+      example.call
+      undef_method :included
+      alias_method :included, :original_included
+    end
+  end
+
+  it 'delegates to the superclass #included method' do
+    # This is the most succinct approach I could think of to test whether the
+    # superclass#included method is called. All of the built-in rspec helpers
+    # did not seem to work for this.
+    included = false
+    superclass.class_eval { define_method(:included) { |_| included = true } }
+    expect { subject }.to change { included }.from(false).to(true)
+  end
+
+  it 'includes methods into the descendant' do
+    subject
+    expect(descendant.included_modules).to include(described_class::Methods)
+  end
+end