JUnit5 with Mockito using @ExtendWith (#2770)

* JUnit5 with Mockito using @ExtendWith

* rename method:
givenUserWithExistingName_whenSaveUser_thenGiveUsernameAlreadyExistsError

rename this class according to the standard -- UserServiceUnitTest.java

junit5/pom.xml

@@ -19,11 +19,12 @@
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <java.version>1.8</java.version>
-        <junit.jupiter.version>5.0.0-RC2</junit.jupiter.version>
+        <junit.jupiter.version>5.0.1</junit.jupiter.version>
-        <junit.platform.version>1.0.0-RC2</junit.platform.version>
+        <junit.platform.version>1.0.1</junit.platform.version>
-        <junit.vintage.version>4.12.0-RC2</junit.vintage.version>
+        <junit.vintage.version>4.12.1</junit.vintage.version>
         <log4j2.version>2.8.2</log4j2.version>
         <h2.version>1.4.196</h2.version>
+        <mockito.version>2.11.0</mockito.version>
 
         <maven-compiler-plugin.version>3.6.0</maven-compiler-plugin.version>
         <maven-surefire-plugin.version>2.19.1</maven-surefire-plugin.version>

junit5/src/main/java/com/baeldung/junit5/mockito/User.java

@@ -0,0 +1,41 @@
+package com.baeldung.junit5.mockito;
+
+public class User {
+    
+    private Integer id;
+    private String name;
+    private int age;
+    
+    public User() {
+    }
+    
+    public User(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+    
+    public Integer getId() {
+        return id;
+    }
+    public void setId(Integer id) {
+        this.id = id;
+    }
+    public String getName() {
+        return name;
+    }
+    public void setName(String name) {
+        this.name = name;
+    }
+    public int getAge() {
+        return age;
+    }
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    @Override
+    public String toString() {
+        return "User [id=" + id + ", name=" + name + ", age=" + age + "]";
+    }
+
+}

junit5/src/main/java/com/baeldung/junit5/mockito/repository/MailClient.java

@@ -0,0 +1,9 @@
+package com.baeldung.junit5.mockito.repository;
+
+import com.baeldung.junit5.mockito.User;
+
+public interface MailClient {
+
+    void sendUserRegistrationMail(User user);
+    
+}

junit5/src/main/java/com/baeldung/junit5/mockito/repository/SettingRepository.java

@@ -0,0 +1,9 @@
+package com.baeldung.junit5.mockito.repository;
+
+public interface SettingRepository {
+    
+    int getUserMinAge();
+
+    int getUserNameMinLength();
+
+}

junit5/src/main/java/com/baeldung/junit5/mockito/repository/UserRepository.java

@@ -0,0 +1,10 @@
+package com.baeldung.junit5.mockito.repository;
+
+import com.baeldung.junit5.mockito.User;
+
+public interface UserRepository {
+
+    User insert(User user);
+    boolean isUsernameAlreadyExists(String userName);
+    
+}

junit5/src/main/java/com/baeldung/junit5/mockito/service/DefaultUserService.java

@@ -0,0 +1,46 @@
+package com.baeldung.junit5.mockito.service;
+
+import com.baeldung.junit5.mockito.User;
+import com.baeldung.junit5.mockito.repository.MailClient;
+import com.baeldung.junit5.mockito.repository.SettingRepository;
+import com.baeldung.junit5.mockito.repository.UserRepository;
+
+public class DefaultUserService implements UserService {
+    
+    private UserRepository userRepository;
+    private SettingRepository settingRepository;
+    private MailClient mailClient;
+    
+    public DefaultUserService(UserRepository userRepository, SettingRepository settingRepository, MailClient mailClient) {
+        this.userRepository = userRepository;
+        this.settingRepository = settingRepository;
+        this.mailClient = mailClient;
+    }
+
+    @Override
+    public User register(User user) {
+        validate(user);
+        User insertedUser = userRepository.insert(user);
+        mailClient.sendUserRegistrationMail(insertedUser);
+        return insertedUser;
+    }
+
+    private void validate(User user) {
+        if(user.getName() == null) {
+            throw new RuntimeException(Errors.USER_NAME_REQUIRED);
+        }
+
+        if(user.getName().length() < settingRepository.getUserNameMinLength()) {
+            throw new RuntimeException(Errors.USER_NAME_SHORT);
+        }
+        
+        if(user.getAge() < settingRepository.getUserMinAge()) {
+            throw new RuntimeException(Errors.USER_AGE_YOUNG);
+        }
+        
+        if(userRepository.isUsernameAlreadyExists(user.getName())) {
+            throw new RuntimeException(Errors.USER_NAME_DUPLICATE);
+        }
+    }
+
+}

junit5/src/main/java/com/baeldung/junit5/mockito/service/Errors.java

@@ -0,0 +1,10 @@
+package com.baeldung.junit5.mockito.service;
+
+public class Errors {
+
+    public static final String USER_NAME_REQUIRED = "user.name.required";
+    public static final String USER_NAME_SHORT = "user.name.short";
+    public static final String USER_AGE_YOUNG = "user.age.young";
+    public static final String USER_NAME_DUPLICATE = "user.name.duplicate";
+    
+}

junit5/src/main/java/com/baeldung/junit5/mockito/service/UserService.java

@@ -0,0 +1,9 @@
+package com.baeldung.junit5.mockito.service;
+
+import com.baeldung.junit5.mockito.User;
+
+public interface UserService {
+    
+    User register(User user);
+
+}

junit5/src/test/java/com/baeldung/junit5/mockito/MockitoExtension.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2015-2016 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v1.0 which
+ * accompanies this distribution and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v10.html
+ */
+
+package com.baeldung.junit5.mockito;
+
+import static org.mockito.Mockito.mock;
+
+import java.lang.reflect.Parameter;
+
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.api.extension.ExtensionContext.Namespace;
+import org.junit.jupiter.api.extension.ExtensionContext.Store;
+import org.junit.jupiter.api.extension.ParameterContext;
+import org.junit.jupiter.api.extension.ParameterResolver;
+import org.junit.jupiter.api.extension.TestInstancePostProcessor;
+import org.mockito.MockitoAnnotations;
+import org.mockito.Mock;
+
+/**
+ * {@code MockitoExtension} showcases the {@link TestInstancePostProcessor}
+ * and {@link ParameterResolver} extension APIs of JUnit 5 by providing
+ * dependency injection support at the field level and at the method parameter
+ * level via Mockito 2.x's {@link Mock @Mock} annotation.
+ *
+ * @since 5.0
+ */
+public class MockitoExtension implements TestInstancePostProcessor, ParameterResolver {
+
+    @Override
+    public void postProcessTestInstance(Object testInstance, ExtensionContext context) {
+        MockitoAnnotations.initMocks(testInstance);
+    }
+
+    @Override
+    public boolean supportsParameter(ParameterContext parameterContext, ExtensionContext extensionContext) {
+        return parameterContext.getParameter().isAnnotationPresent(Mock.class);
+    }
+
+    @Override
+    public Object resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext) {
+        return getMock(parameterContext.getParameter(), extensionContext);
+    }
+
+    private Object getMock(Parameter parameter, ExtensionContext extensionContext) {
+        Class<?> mockType = parameter.getType();
+        Store mocks = extensionContext.getStore(Namespace.create(MockitoExtension.class, mockType));
+        String mockName = getMockName(parameter);
+
+        if (mockName != null) {
+            return mocks.getOrComputeIfAbsent(mockName, key -> mock(mockType, mockName));
+        }
+        else {
+            return mocks.getOrComputeIfAbsent(mockType.getCanonicalName(), key -> mock(mockType));
+        }
+    }
+
+    private String getMockName(Parameter parameter) {
+        String explicitMockName = parameter.getAnnotation(Mock.class).name().trim();
+        if (!explicitMockName.isEmpty()) {
+            return explicitMockName;
+        }
+        else if (parameter.isNamePresent()) {
+            return parameter.getName();
+        }
+        return null;
+    }
+
+}

junit5/src/test/java/com/baeldung/junit5/mockito/UserServiceUnitTest.java

@@ -0,0 +1,122 @@
+package com.baeldung.junit5.mockito;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.fail;
+import static org.mockito.ArgumentMatchers.any;
+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;
+import org.junit.platform.runner.JUnitPlatform;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
+
+import com.baeldung.junit5.mockito.repository.MailClient;
+import com.baeldung.junit5.mockito.repository.SettingRepository;
+import com.baeldung.junit5.mockito.repository.UserRepository;
+import com.baeldung.junit5.mockito.service.DefaultUserService;
+import com.baeldung.junit5.mockito.service.Errors;
+import com.baeldung.junit5.mockito.service.UserService;
+
+@RunWith(JUnitPlatform.class)
+@ExtendWith(MockitoExtension.class)
+public class UserServiceUnitTest {
+    
+    UserService userService;
+    @Mock UserRepository userRepository;
+    
+    User user;
+    
+    @BeforeEach
+    void init(@Mock SettingRepository settingRepository, @Mock MailClient mailClient) {
+        userService = new DefaultUserService(userRepository, settingRepository, mailClient);
+        when(settingRepository.getUserMinAge()).thenReturn(10);
+        when(settingRepository.getUserNameMinLength()).thenReturn(4);
+        when(userRepository.isUsernameAlreadyExists(any(String.class))).thenReturn(false);
+    }
+    
+    @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);
+                user.setId(sequence++);
+                return user;
+            }
+        });
+        
+        // When
+        User insertedUser = userService.register(user);
+        
+        // Then
+        verify(userRepository).insert(user);
+        Assertions.assertNotNull(user.getId());
+        verify(mailClient).sendUserRegistrationMail(insertedUser);
+    }
+
+    @Test
+    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);
+        }
+        
+        // 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);
+        }
+        
+        // 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);
+        }
+        
+        // Then
+        verify(userRepository, never()).insert(user);
+    }
+    
+}