Add specs for problem described in issue

ee/spec/controllers/groups/group_members_controller_spec.rb

@@ -57,6 +57,55 @@ RSpec.describe Groups::GroupMembersController do
       enable_external_authorization_service_check
     end
 
+    describe 'PUT #update' do
+      context 'when group has email domain feature enabled' do
+        let(:email) { 'test@gitlab.com' }
+        let(:member_user) { create(:user, email: email) }
+        let(:member) { group.add_guest(member_user) }
+
+        before do
+          stub_licensed_features(group_allowed_email_domains: true)
+          create(:allowed_email_domain, group: group)
+        end
+
+        subject do
+          put :update, xhr: true, params: {
+                                            group_member: {
+                                              access_level: 50
+                                            },
+                                            group_id: group,
+                                            id: member
+                                          }
+        end
+
+        context 'for a user with an email belonging to the allowed domain' do
+          it 'returns error status' do
+            subject
+
+            expect(response).to have_gitlab_http_status(:ok)
+          end
+        end
+
+        context 'for a user with an un-verified email belonging to a domain different from the allowed domain' do
+          let(:email) { 'test@gmail.com' }
+
+          context 'for a user with an email belonging to the allowed domain' do
+            it 'returns error status' do
+              subject
+
+              expect(response).to have_gitlab_http_status(:unprocessable_entity)
+            end
+
+            it 'returns error message' do
+              subject
+
+              expect(json_response).to eq({ 'message' => "User email 'test@gmail.com' does not match the allowed domains of gitlab.com" })
+            end
+          end
+        end
+      end
+    end
+
     describe 'POST #override' do
       let(:group) { create(:group_with_ldap_group_link) }