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Java Mockito 快速入门指南 Mock是指使用Mockito创建的模拟对象，它模拟真实对象的行为，用于替代真实对象的依赖项，以便进行独立的单元测试

发布时间 2023-12-07 18:29:33作者: sunny123456

Java Mockito 快速入门指南 Mock是指使用Mockito创建的模拟对象，它模拟真实对象的行为，用于替代真实对象的依赖项，以便进行独立的单元测试

在软件开发中，单元测试对于确保代码的正确性和可靠性至关重要。Mockito是一个强大的Java测试框架，它提供了丰富的功能和方法，使得编写模拟测试变得简单而高效。本文将介绍Mockito的基础使用方法，包括常用的方法和注解，并通过两个简单到困难的示例演示其用法。

常用方法

当使用Mockito进行单元测试时，以下是几个常用的Mockito方法和概念：

  • mock()/@Mock：

    • Mock是指使用Mockito创建的模拟对象，它模拟真实对象的行为，用于替代真实对象的依赖项，以便进行独立的单元测试。

  • spy()/@Spy：

    • Spy是指使用Mockito创建的部分模拟对象，它保留了真实对象的部分行为。Spy对象既可以模拟方法的返回值，也可以保留方法的实际行为。

  • @InjectMocks：

    • @InjectMocks是一个Mockito注解，用于自动将模拟对象注入到被测对象中的相应字段中。

  • doReturn()：

    • doReturn()方法用于为模拟对象设置方法调用的返回值，可以覆盖默认行为。

  • when()：

    • when()方法用于指定模拟对象的方法调用，并设置相应的操作，例如返回值、异常等。

  • verify()：

    • verify()方法用于验证模拟对象的方法是否被调用，并可以进一步验证方法的调用次数和参数。

  • Stub：

    • Stub翻译成打桩，是指为模拟对象设置预定义的行为或返回值，使其在测试过程中按照期望的方式运行。

调用方式

在Mockito中，可以通过函数调用和注解两种方式来应用模拟对象。这两种方式在语法和使用上略有不同，下面将介绍它们的应用区别：

函数调用方式

使用函数调用方式，需要手动创建和管理模拟对象。
通过调用Mockito.mock()方法创建模拟对象，并使用各种when()、thenReturn()、verify()等函数来定义模拟对象的行为和验证。
函数调用方式更加灵活，可以在测试方法的任意位置创建和配置模拟对象。
示例代码：

List<String> mockedList = Mockito.mock(List.class);
Mockito.when(mockedList.get(0)).thenReturn("Mocked Value");
String result = mockedList.get(0);
Mockito.verify(mockedList).get(0);

注解方式

使用注解方式，可以通过注解来自动创建和注入模拟对象。
使用@Mock注解在测试类中声明模拟对象的字段，然后使用@InjectMocks注解将模拟对象自动注入到被测对象中。
注解方式更加简洁和便捷，省去了手动创建和配置模拟对象的步骤。

  • 需要注意，通过注解的方式，需要在 @Before test前显示声明 MockitoAnnotations.initMocks(this);

示例代码：

public class MyTestClass {
    @Mock
    private List<String> mockedList;

<span class="token annotation punctuation">@InjectMocks</span>
<span class="token keyword">private</span> <span class="token class-name">MyClass</span> myClass<span class="token punctuation">;</span>

<span class="token annotation punctuation">@Before</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">setup</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token class-name">MockitoAnnotations</span><span class="token punctuation">.</span><span class="token function">initMocks</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testMethod</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token class-name">Mockito</span><span class="token punctuation">.</span><span class="token function">when</span><span class="token punctuation">(</span>mockedList<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">thenReturn</span><span class="token punctuation">(</span><span class="token string">"Mocked Value"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">String</span> result <span class="token operator">=</span> myClass<span class="token punctuation">.</span><span class="token function">myMethod</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Mockito</span><span class="token punctuation">.</span><span class="token function">verify</span><span class="token punctuation">(</span>mockedList<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>



}

使用方法1

上面只是做了一个简单的介绍，下面我们结合一些例子来看看如何使用。

我们将创建一个示例来测试一个银行应用中的账户服务。假设我们有一个AccountService类，它依赖于AccountRepository和NotificationService来执行一些操作。我们将使用Mockito来模拟这些依赖项，并测试AccountService的方法。

首先，让我们创建一个名为AccountService的类：

public class AccountService {
    private AccountRepository accountRepository;
    private NotificationService notificationService;

<span class="token keyword">public</span> <span class="token class-name">AccountService</span><span class="token punctuation">(</span><span class="token class-name">AccountRepository</span> accountRepository<span class="token punctuation">,</span> <span class="token class-name">NotificationService</span> notificationService<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span>accountRepository <span class="token operator">=</span> accountRepository<span class="token punctuation">;</span>
    <span class="token keyword">this</span><span class="token punctuation">.</span>notificationService <span class="token operator">=</span> notificationService<span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">deposit</span><span class="token punctuation">(</span><span class="token class-name">String</span> accountId<span class="token punctuation">,</span> <span class="token keyword">double</span> amount<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token class-name">Account</span> account <span class="token operator">=</span> accountRepository<span class="token punctuation">.</span><span class="token function">findById</span><span class="token punctuation">(</span>accountId<span class="token punctuation">)</span><span class="token punctuation">;</span>
    account<span class="token punctuation">.</span><span class="token function">deposit</span><span class="token punctuation">(</span>amount<span class="token punctuation">)</span><span class="token punctuation">;</span>
    accountRepository<span class="token punctuation">.</span><span class="token function">save</span><span class="token punctuation">(</span>account<span class="token punctuation">)</span><span class="token punctuation">;</span>
    notificationService<span class="token punctuation">.</span><span class="token function">sendNotification</span><span class="token punctuation">(</span><span class="token string">"Deposit successful"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>



}

接下来，我们将创建一个名为AccountRepository的接口和一个名为NotificationService的接口作为依赖项：

public interface AccountRepository {
    Account findById(String accountId);

<span class="token keyword">void</span> <span class="token function">save</span><span class="token punctuation">(</span><span class="token class-name">Account</span> account<span class="token punctuation">)</span><span class="token punctuation">;</span>



}


public interface NotificationService {

void sendNotification(String message);

}

然后，我们编写一个测试类AccountServiceTest，使用Mockito来模拟AccountRepository和NotificationService，并测试AccountService的deposit()方法。

import org.junit.Assert;
import org.junit.Test;
import org.mockito.Mockito;

public class AccountServiceTest {


<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testDeposit</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// 创建模拟对象</span>
    <span class="token class-name">AccountRepository</span> accountRepositoryMock <span class="token operator">=</span> <span class="token class-name">Mockito</span><span class="token punctuation">.</span><span class="token function">mock</span><span class="token punctuation">(</span><span class="token class-name">AccountRepository</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">NotificationService</span> notificationServiceMock <span class="token operator">=</span> <span class="token class-name">Mockito</span><span class="token punctuation">.</span><span class="token function">mock</span><span class="token punctuation">(</span><span class="token class-name">NotificationService</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    
    <span class="token comment">// 创建被测对象并注入模拟对象</span>
    <span class="token class-name">AccountService</span> accountService <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">AccountService</span><span class="token punctuation">(</span>accountRepositoryMock<span class="token punctuation">,</span> notificationServiceMock<span class="token punctuation">)</span><span class="token punctuation">;</span>
    
    <span class="token comment">// 创建模拟账户</span>
    <span class="token class-name">Account</span> account <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Account</span><span class="token punctuation">(</span><span class="token string">"1234567890"</span><span class="token punctuation">,</span> <span class="token number">1000.0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    
    <span class="token comment">// 设置模拟对象的行为</span>
    <span class="token class-name">Mockito</span><span class="token punctuation">.</span><span class="token function">when</span><span class="token punctuation">(</span>accountRepositoryMock<span class="token punctuation">.</span><span class="token function">findById</span><span class="token punctuation">(</span><span class="token string">"1234567890"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">thenReturn</span><span class="token punctuation">(</span>account<span class="token punctuation">)</span><span class="token punctuation">;</span>
    
    <span class="token comment">// 调用被测方法</span>
    accountService<span class="token punctuation">.</span><span class="token function">deposit</span><span class="token punctuation">(</span><span class="token string">"1234567890"</span><span class="token punctuation">,</span> <span class="token number">500.0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    
    <span class="token comment">// 验证结果</span>
    <span class="token class-name">Assert</span><span class="token punctuation">.</span><span class="token function">assertEquals</span><span class="token punctuation">(</span><span class="token number">1500.0</span><span class="token punctuation">,</span> account<span class="token punctuation">.</span><span class="token function">getBalance</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">0.01</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    
    <span class="token comment">// 验证模拟对象的方法是否被调用</span>
    <span class="token class-name">Mockito</span><span class="token punctuation">.</span><span class="token function">verify</span><span class="token punctuation">(</span>accountRepositoryMock<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">save</span><span class="token punctuation">(</span>account<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Mockito</span><span class="token punctuation">.</span><span class="token function">verify</span><span class="token punctuation">(</span>notificationServiceMock<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">sendNotification</span><span class="token punctuation">(</span><span class="token string">"Deposit successful"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>



}

在这个示例中，我们首先使用Mockito.mock()方法创建了一个名为accountRepositoryMock的模拟对象和一个名为notificationServiceMock的模拟对象。然后，我们创建了AccountService的实例，并使用模拟对象进行依赖项注入。

接下来，我们创建了一个名为account的模拟账户，并使用Mockito.when().thenReturn()方法为模拟对象的findById()方法设置了存根，以返回模拟账户。然后，我们调用accountService.deposit()方法进行测试，并使用Assert.assertEquals()方法验证账户的余额是否正确更新。

最后，我们使用Mockito.verify()方法验证模拟对象的save()方法和sendNotification()方法是否被调用。

通过这个示例，我们演示了如何使用Mockito的函数调用方式进行复杂的模拟测试。使用Mockito的各种函数，我们可以方便地设置模拟对象的行为、验证方法的调用，并确保被测代码的正确性。

使用方法2

当使用Spring Boot进行开发时，我们经常会使用 @Component 或者 @Autowired 的方式进行开发，下面介绍如何使用Mockito和注解的方式来对带有依赖注入的Spring组件进行测试。

下面是一个示例，展示了如何使用Mockito和注解对带有依赖注入的AccountService进行测试。

首先，让我们定义AccountService类并添加@Component注解：

@Component
public class AccountService {
    @Autowired
    private AccountRepository accountRepository;
    @Autowired
    private NotificationService notificationService;

<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">deposit</span><span class="token punctuation">(</span><span class="token class-name">String</span> accountId<span class="token punctuation">,</span> <span class="token keyword">double</span> amount<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token class-name">Account</span> account <span class="token operator">=</span> accountRepository<span class="token punctuation">.</span><span class="token function">findById</span><span class="token punctuation">(</span>accountId<span class="token punctuation">)</span><span class="token punctuation">;</span>
    account<span class="token punctuation">.</span><span class="token function">deposit</span><span class="token punctuation">(</span>amount<span class="token punctuation">)</span><span class="token punctuation">;</span>
    accountRepository<span class="token punctuation">.</span><span class="token function">save</span><span class="token punctuation">(</span>account<span class="token punctuation">)</span><span class="token punctuation">;</span>
    notificationService<span class="token punctuation">.</span><span class="token function">sendNotification</span><span class="token punctuation">(</span><span class="token string">"Deposit successful"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>



}

接下来，我们将编写一个名为AccountServiceTest的测试类，使用Mockito和注解对AccountService进行测试。

import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.junit.MockitoJUnitRunner;

@RunWith(MockitoJUnitRunner.class)

public class AccountServiceTest {

@Mock

private AccountRepository accountRepositoryMock;


<span class="token annotation punctuation">@Mock</span>
<span class="token keyword">private</span> <span class="token class-name">NotificationService</span> notificationServiceMock<span class="token punctuation">;</span>

<span class="token annotation punctuation">@InjectMocks</span>
<span class="token keyword">private</span> <span class="token class-name">AccountService</span> accountService<span class="token punctuation">;</span>

<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testDeposit</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// 创建模拟账户</span>
    <span class="token class-name">Account</span> account <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Account</span><span class="token punctuation">(</span><span class="token string">"1234567890"</span><span class="token punctuation">,</span> <span class="token number">1000.0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    
    <span class="token comment">// 设置模拟对象的行为</span>
    <span class="token class-name">Mockito</span><span class="token punctuation">.</span><span class="token function">when</span><span class="token punctuation">(</span>accountRepositoryMock<span class="token punctuation">.</span><span class="token function">findById</span><span class="token punctuation">(</span><span class="token string">"1234567890"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">thenReturn</span><span class="token punctuation">(</span>account<span class="token punctuation">)</span><span class="token punctuation">;</span>
    
    <span class="token comment">// 调用被测方法</span>
    accountService<span class="token punctuation">.</span><span class="token function">deposit</span><span class="token punctuation">(</span><span class="token string">"1234567890"</span><span class="token punctuation">,</span> <span class="token number">500.0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    
    <span class="token comment">// 验证结果</span>
    <span class="token class-name">Assert</span><span class="token punctuation">.</span><span class="token function">assertEquals</span><span class="token punctuation">(</span><span class="token number">1500.0</span><span class="token punctuation">,</span> account<span class="token punctuation">.</span><span class="token function">getBalance</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token number">0.01</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    
    <span class="token comment">// 验证模拟对象的方法是否被调用</span>
    <span class="token class-name">Mockito</span><span class="token punctuation">.</span><span class="token function">verify</span><span class="token punctuation">(</span>accountRepositoryMock<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">save</span><span class="token punctuation">(</span>account<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Mockito</span><span class="token punctuation">.</span><span class="token function">verify</span><span class="token punctuation">(</span>notificationServiceMock<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">sendNotification</span><span class="token punctuation">(</span><span class="token string">"Deposit successful"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>



}

在这个示例中，我们使用了@RunWith(MockitoJUnitRunner.class)注解来启用Mockito框架的支持。这个注解会为我们自动初始化模拟对象和被测对象。

使用@Mock注解，我们创建了名为accountRepositoryMock和notificationServiceMock的模拟对象。使用@InjectMocks注解，我们将这些模拟对象注入到accountService对象中。

然后，我们使用Mockito.when().thenReturn()方法设置模拟对象的行为，并调用accountService.deposit()方法进行测试。最后，我们使用Assert.assertEquals()方法验证结果，并使用Mockito.verify()方法验证模拟对象的方法是否被调用。

通过这个示例，我们展示了如何使用Mockito和注解的方式对带有依赖注入的Spring组件进行测试。Mockito和注解的结合可以方便地创建和注入模拟对象，使测试更加简洁和可读。

以上就是一些Java Mockito的简单使用方法啦~ 如有问题，欢迎来交流~

Reference

原文链接：https://www.jianshu.com/p/1127afe26839