diff --git a/testing-modules/mockito-simple/src/test/java/com/baeldung/junit5/mockito/UserServiceUnitTest.java b/testing-modules/mockito-simple/src/test/java/com/baeldung/junit5/mockito/UserServiceUnitTest.java
index 6aa3dd4a7f..07fc96f11e 100644
--- a/testing-modules/mockito-simple/src/test/java/com/baeldung/junit5/mockito/UserServiceUnitTest.java
+++ b/testing-modules/mockito-simple/src/test/java/com/baeldung/junit5/mockito/UserServiceUnitTest.java
@@ -1,6 +1,7 @@
 package com.baeldung.junit5.mockito;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.fail;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.lenient;
@@ -8,7 +9,6 @@ import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
-import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
@@ -26,31 +26,38 @@ import com.baeldung.junit5.mockito.service.Errors;
 import com.baeldung.junit5.mockito.service.UserService;
 
 @ExtendWith(MockitoExtension.class)
-public class UserServiceUnitTest {
-    
+class UserServiceUnitTest {
+
     UserService userService;
+    
     SettingRepository settingRepository;
-    @Mock UserRepository userRepository;
-    @Mock MailClient mailClient;
+    
+    @Mock
+    UserRepository userRepository;
+    
+    @Mock
+    MailClient mailClient;
 
     User user;
-    
+
     @BeforeEach
     void init(@Mock SettingRepository settingRepository) {
         userService = new DefaultUserService(userRepository, settingRepository, mailClient);
-        lenient().when(settingRepository.getUserMinAge()).thenReturn(10);
+        lenient().when(settingRepository.getUserMinAge())
+            .thenReturn(10);
         when(settingRepository.getUserNameMinLength()).thenReturn(4);
-        lenient().when(userRepository.isUsernameAlreadyExists(any(String.class))).thenReturn(false);
+        lenient().when(userRepository.isUsernameAlreadyExists(any(String.class)))
+            .thenReturn(false);
         this.settingRepository = settingRepository;
     }
-    
+
     @Test
     void givenValidUser_whenSaveUser_thenSucceed(@Mock MailClient mailClient) {
         // Given
         user = new User("Jerry", 12);
         when(userRepository.insert(any(User.class))).then(new Answer<User>() {
             int sequence = 1;
-            
+
             @Override
             public User answer(InvocationOnMock invocation) throws Throwable {
                 User user = (User) invocation.getArgument(0);
@@ -63,10 +70,10 @@ public class UserServiceUnitTest {
 
         // When
         User insertedUser = userService.register(user);
-        
+
         // Then
         verify(userRepository).insert(user);
-        Assertions.assertNotNull(user.getId());
+        assertNotNull(user.getId());
         verify(mailClient).sendUserRegistrationMail(insertedUser);
     }
 
@@ -74,53 +81,53 @@ public class UserServiceUnitTest {
     void givenShortName_whenSaveUser_thenGiveShortUsernameError() {
         // Given
         user = new User("tom", 12);
-        
+
         // When
         try {
             userService.register(user);
             fail("Should give an error");
-        } catch(Exception ex) {
-            assertEquals(ex.getMessage(), Errors.USER_NAME_SHORT);
+        } catch (Exception ex) {
+            assertThat(ex.getMessage()).isEqualTo(Errors.USER_NAME_SHORT);
         }
-        
+
         // Then
         verify(userRepository, never()).insert(user);
     }
-    
+
     @Test
     void givenSmallAge_whenSaveUser_thenGiveYoungUserError() {
         // Given
         user = new User("jerry", 3);
-        
+
         // When
         try {
             userService.register(user);
             fail("Should give an error");
-        } catch(Exception ex) {
-            assertEquals(ex.getMessage(), Errors.USER_AGE_YOUNG);
+        } catch (Exception ex) {
+            assertThat(ex.getMessage()).isEqualTo(Errors.USER_AGE_YOUNG);
         }
-        
+
         // Then
         verify(userRepository, never()).insert(user);
     }
-    
+
     @Test
     void givenUserWithExistingName_whenSaveUser_thenGiveUsernameAlreadyExistsError() {
         // Given
         user = new User("jerry", 12);
         Mockito.reset(userRepository);
         when(userRepository.isUsernameAlreadyExists(any(String.class))).thenReturn(true);
-        
+
         // When
         try {
             userService.register(user);
             fail("Should give an error");
-        } catch(Exception ex) {
-            assertEquals(ex.getMessage(), Errors.USER_NAME_DUPLICATE);
+        } catch (Exception ex) {
+            assertThat(ex.getMessage()).isEqualTo(Errors.USER_NAME_DUPLICATE);
         }
-        
+
         // Then
         verify(userRepository, never()).insert(user);
     }
-    
+
 }