Add tests for notification module

src/test/java/com/openisle/service/NotificationServiceTest.java

@@ -0,0 +1,63 @@
+package com.openisle.service;
+
+import com.openisle.model.Notification;
+import com.openisle.model.User;
+import com.openisle.repository.NotificationRepository;
+import com.openisle.repository.UserRepository;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+
+import java.util.List;
+import java.util.Optional;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.*;
+
+class NotificationServiceTest {
+
+    @Test
+    void markReadUpdatesOnlyOwnedNotifications() {
+        NotificationRepository nRepo = mock(NotificationRepository.class);
+        UserRepository uRepo = mock(UserRepository.class);
+        NotificationService service = new NotificationService(nRepo, uRepo);
+
+        User user = new User();
+        user.setId(1L);
+        user.setUsername("alice");
+        when(uRepo.findByUsername("alice")).thenReturn(Optional.of(user));
+
+        Notification n1 = new Notification();
+        n1.setId(10L);
+        n1.setUser(user);
+        Notification n2 = new Notification();
+        n2.setId(11L);
+        n2.setUser(user);
+        when(nRepo.findAllById(List.of(10L, 11L))).thenReturn(List.of(n1, n2));
+
+        service.markRead("alice", List.of(10L, 11L));
+
+        assertTrue(n1.isRead());
+        assertTrue(n2.isRead());
+        verify(nRepo).saveAll(List.of(n1, n2));
+    }
+
+    @Test
+    void listNotificationsWithoutFilter() {
+        NotificationRepository nRepo = mock(NotificationRepository.class);
+        UserRepository uRepo = mock(UserRepository.class);
+        NotificationService service = new NotificationService(nRepo, uRepo);
+
+        User user = new User();
+        user.setId(2L);
+        user.setUsername("bob");
+        when(uRepo.findByUsername("bob")).thenReturn(Optional.of(user));
+
+        Notification n = new Notification();
+        when(nRepo.findByUserOrderByCreatedAtDesc(user)).thenReturn(List.of(n));
+
+        List<Notification> list = service.listNotifications("bob", null);
+
+        assertEquals(1, list.size());
+        verify(nRepo).findByUserOrderByCreatedAtDesc(user);
+    }
+}