FEATURE: provide more details when performing a bulk add to group

spec/controllers/admin/groups_controller_spec.rb

@@ -69,6 +69,11 @@ describe Admin::GroupsController do
       expect(user2.primary_group).to eq(group)
       expect(user2.title).to eq("WAT")
       expect(user2.trust_level).to eq(4)
+
+      # verify JSON response
+      json = ::JSON.parse(response.body)
+      expect(json['message']).to eq("2 users have been added to the group.")
+      expect(json['users_not_added'][0]).to eq("doesnt_exist")
     end
   end