OZG-3841 implement comments from code review

notification-manager/src/main/java/de/itvsh/kop/notification/user/UserNotificationService.java

@@ -34,6 +34,7 @@ import org.springframework.stereotype.Service;
 import de.itvsh.kop.notification.email.EmailRemoteService;
 import de.itvsh.kop.notification.email.UserEmail;
 import de.itvsh.kop.notification.vorgang.Vorgang;
+import lombok.NonNull;
 
 @Service
 public class UserNotificationService {
@@ -48,7 +49,7 @@ public class UserNotificationService {
 	private UserRemoteService userRemoteService;
 
 	@Async
-	public void sendNotification(Vorgang vorgang) {
+	public void sendNotification(@NonNull Vorgang vorgang) {
 		if (nonNull(vorgang.getOrganisationseinheitenId())) {
 			var recipients = userRemoteService.getRecipients(vorgang.getOrganisationseinheitenId());
 			emailRemoteService.sendEmail(buildUserEmail(recipients, MAIL_SUBJECT_TEMPLATE.formatted(vorgang.getVorgangName())));

notification-manager/src/test/java/de/itvsh/kop/notification/user/UserNotificationServiceTest.java

@@ -23,6 +23,7 @@
  */
 package de.itvsh.kop.notification.user;
 
+import static org.assertj.core.api.Assertions.*;
 import static org.mockito.ArgumentMatchers.*;
 import static org.mockito.Mockito.*;
 
@@ -88,7 +89,7 @@ class UserNotificationServiceTest {
 			void shouldSetSubject() {
 				service.sendNotification(VorgangTestFactory.create());
 
-				verify(service).buildUserEmail(anyList(), eq(UserNotificationService.MAIL_SUBJECT_TEMPLATE.formatted(VorgangTestFactory.VORGANG_NAME)));
+				verify(service).buildUserEmail(anyList(), eq("Neuer Vorgang: " + VorgangTestFactory.VORGANG_NAME));
 
 			}
 		}
@@ -113,5 +114,12 @@ class UserNotificationServiceTest {
 				verify(emailRemoteService, never()).sendEmail(any(UserEmail.class));
 			}
 		}
+
+		@Test
+		void shouldThrowExceptionWhenVorgangNull() {
+			assertThatThrownBy(() -> service.sendNotification(null))
+					.withFailMessage("organisationsEinheitId cannot be null.")
+					.isInstanceOf(IllegalArgumentException.class);
+		}
 	}
 }
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