Support id method in Factory.

lib/factory_girl/factory.rb

@@ -1,4 +1,5 @@
 class Factory
+  undef :id
   undef :type
 
   # Raised when a factory is defined that attempts to instantiate itself.

spec/factory_girl/factory_spec.rb

@@ -77,6 +77,21 @@
       attributes.first.name.should == :type
     end
 
+    it "should return static attribute when asked for the id" do
+      result = @factory.id
+      result.should be_kind_of(Array)
+      result.first.should be_kind_of(Factory::Attribute::Static)
+      result.first.name.should == :id
+    end
+
+    it "should define id as an attribute" do
+      @factory.id { "it's an id" }
+      attributes = @factory.attributes
+      attributes.should be_kind_of(Array)
+      attributes.size.should == 1
+      attributes.first.name.should == :id
+    end
+
     it "should not allow the same attribute to be added twice" do
       lambda {
         2.times { @factory.add_attribute :first_name }