Add === support

Closes #341

lib/draper/decoratable.rb

@@ -21,6 +21,10 @@ module Draper::Decoratable
     false
   end
 
+  def ===(other)
+    super || (other.respond_to?(:source) && super(other.source))
+  end
+
   module ClassMethods
     def decorate(options = {})
       decorator_class.decorate_collection(self.scoped, options)
@@ -32,5 +36,9 @@ module Draper::Decoratable
     rescue NameError
       raise Draper::UninferrableDecoratorError.new(self)
     end
+
+    def ===(other)
+      super || (other.respond_to?(:source) && super(other.source))
+    end
   end
 end

spec/draper/decoratable_spec.rb

@@ -45,6 +45,75 @@ describe Draper::Decoratable do
     end
   end
 
+  describe "#===" do
+    context "with itself" do
+      it "returns true" do
+        (subject === subject).should be_true
+      end
+    end
+
+    context "with another instance" do
+      it "returns false" do
+        (subject === Product.new).should be_false
+      end
+    end
+
+    context "with a decorated version of itself" do
+      it "returns true" do
+        decorator = double(source: subject)
+        (subject === decorator).should be_true
+      end
+    end
+
+    context "with a decorated other instance" do
+      it "returns false" do
+        decorator = double(source: Product.new)
+        (subject === decorator).should be_false
+      end
+    end
+  end
+
+  describe ".====" do
+    context "with an instance" do
+      it "returns true" do
+        (Product === Product.new).should be_true
+      end
+    end
+
+    context "with a derived instance" do
+      it "returns true" do
+        (Product === Widget.new).should be_true
+      end
+    end
+
+    context "with an unrelated instance" do
+      it "returns false" do
+        (Product === Object.new).should be_false
+      end
+    end
+
+    context "with a decorated instance" do
+      it "returns true" do
+        decorator = double(source: Product.new)
+        (Product === decorator).should be_true
+      end
+    end
+
+    context "with a decorated derived instance" do
+      it "returns true" do
+        decorator = double(source: Widget.new)
+        (Product === decorator).should be_true
+      end
+    end
+
+    context "with a decorated unrelated instance" do
+      it "returns false" do
+        decorator = double(source: Object.new)
+        (Product === decorator).should be_false
+      end
+    end
+  end
+
   describe ".decorate" do
     it "returns a collection decorator" do
       Product.stub(:scoped).and_return([Product.new])

spec/draper/decorator_spec.rb

@@ -219,9 +219,66 @@ describe Draper::Decorator do
   end
 
   describe "#==" do
-    it "compares the decorated models" do
-      other = Draper::Decorator.new(source)
-      subject.should == other
+    context "with itself" do
+      it "returns true" do
+        (subject == subject).should be_true
+      end
+    end
+
+    context "with another decorator having the same source" do
+      it "returns true" do
+        (subject == ProductDecorator.new(source)).should be_true
+      end
+    end
+
+    context "with another decorator having a different source" do
+      it "returns false" do
+        (subject == ProductDecorator.new(Object.new)).should be_false
+      end
+    end
+
+    context "with the source object" do
+      it "returns true" do
+        (subject == source).should be_true
+      end
+    end
+
+    context "with another object" do
+      it "returns false" do
+        (subject == Object.new).should be_false
+      end
+    end
+  end
+
+  describe "#===" do
+    context "with itself" do
+      it "returns true" do
+        (subject === subject).should be_true
+      end
+    end
+
+    context "with another decorator having the same source" do
+      it "returns true" do
+        (subject === ProductDecorator.new(source)).should be_true
+      end
+    end
+
+    context "with another decorator having a different source" do
+      it "returns false" do
+        (subject === ProductDecorator.new(Object.new)).should be_false
+      end
+    end
+
+    context "with the source object" do
+      it "returns true" do
+        (subject === source).should be_true
+      end
+    end
+
+    context "with another object" do
+      it "returns false" do
+        (subject === Object.new).should be_false
+      end
     end
   end