Test: add unit tests for ActivityLog entity (constructor and prePersist)

src/test/java/org/example/vet1177/entities/ActivityLogTest.java

@@ -0,0 +1,57 @@
+package org.example.vet1177.entities;
+
+import org.junit.jupiter.api.Test;
+
+import java.time.Instant;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.mock;
+
+public class ActivityLogTest {
+
+    @Test
+    void shouldCreateActivityLogCorrectly(){
+
+        //Arrange
+        User user = mock(User.class);
+        MedicalRecord record = mock(MedicalRecord.class);
+
+        ActivityLog log = new ActivityLog(
+                ActivityType.CASE_CREATED,
+                "Created case",
+                user,
+                record
+        );
+
+        //Assert
+        assertEquals(ActivityType.CASE_CREATED, log.getAction());
+        assertEquals("Created case", log.getDescription());
+        assertEquals(user, log.getPerformedBy());
+        assertEquals(record, log.getMedicalRecord());
+
+    }
+
+    @Test
+    void shouldSetCreatedAtOnPrePersist(){
+        //Arrange
+        User user = mock(User.class);
+        MedicalRecord record = mock(MedicalRecord.class);
+
+        ActivityLog log = new ActivityLog(
+                ActivityType.UPDATED,
+                "Updated record",
+                user,
+                record
+        );
+
+        // Act (simulate JPA)
+        Instant before = Instant.now();
+        log.onCreate();
+        Instant after = Instant.now();
+
+        // Assert
+        assertNotNull(log.getCreatedAt());
+        assertTrue(!log.getCreatedAt().isBefore(before));
+        assertTrue(!log.getCreatedAt().isAfter(after));
+    }
+}