Fix more tests

spec/models/work_package_spec.rb

@@ -1037,7 +1037,7 @@ describe WorkPackage, type: :model do
         it { is_expected.not_to be_nil }
       end
 
-      let(:expected_users) { work_package.author.mail }
+      let(:expected_users) { work_package.author }
 
       it_behaves_like 'includes expected users'
     end
@@ -1051,7 +1051,7 @@ describe WorkPackage, type: :model do
         it { is_expected.not_to be_nil }
       end
 
-      let(:expected_users) { work_package.assigned_to.mail }
+      let(:expected_users) { work_package.assigned_to }
 
       it_behaves_like 'includes expected users'
     end

spec/support/shared/acts_as_watchable.rb

@@ -133,7 +133,7 @@ MESSAGE
 
     subject { model_instance.watcher_recipients }
 
-    it { is_expected.to match_array([watching_user.mail]) }
+    it { is_expected.to match_array([watching_user]) }
 
     context 'when the permission to watch has been removed' do
       before do