Add MongoidAdapter specs for unsaved instances

spec/cancan/model_adapters/mongoid_adapter_spec.rb

@@ -135,6 +135,18 @@ if ENV["MODEL_ADAPTER"] == "mongoid"
           obj2 = MongoidProject.create(:age => 40)
           @ability.can?(:read, obj2).should == false
         end
+        
+        it "should handle instance not saved to database" do
+          obj = MongoidProject.new(:title => 'Sir')
+          @ability.can :read, MongoidProject, :title.in => ["Sir", "Madam"]
+          @ability.can?(:read, obj).should == true
+          
+          # accessible_by only returns saved records
+          MongoidProject.accessible_by(@ability, :read).entries.should == []
+          
+          obj2 = MongoidProject.new(:title => 'Lord')
+          @ability.can?(:read, obj2).should == false
+        end          
       end
 
       it "should call where with matching ability conditions" do