.id         @node_group_a.save          @node_group_a.should_not be_valid         @node_group_a.errors.full_messages.should include("Validation failed: Creating a dependency from group 'A' to group 'B' creates a cycle")         @node_group_a.node_groups.should be_empty       end        it "should allow a group to be included twice through inheritance" do         @node_group_c = create(:node_group)         @node_group_d = create(:node_group)         @node_group_a.node_groups << @node_group_c         @node_group_b.node_groups << @node_group_c         @node_group_d.assigned_node_group_