Mockito 如何捕获传递给注入的模拟对象方法的参数？

Question

我正在尝试测试服务 class，它在内部使用 Spring AMQP 连接对象。此连接对象由 Spring 注入。但是，我不希望我的单元测试实际与 AMQP 代理通信，所以我使用 Mockito 注入连接对象的模拟。

/** 
 * The real service class being tested.  Has an injected dependency. 
 */ 
public class UserService {

   @Autowired
   private AmqpTemplate amqpTemplate;

   public final String doSomething(final String inputString) {
      final String requestId = UUID.randomUUID().toString();
      final Message message = ...;
      amqpTemplate.send(requestId, message);
      return requestId;
   }
}

/** 
 * Unit test 
 */
public class UserServiceTest {

   /** This is the class whose real code I want to test */
   @InjectMocks
   private UserService userService;

   /** This is a dependency of the real class, that I wish to override with a mock */
   @Mock
   private AmqpTemplate amqpTemplateMock;

   @Before
   public void initMocks() {
      MockitoAnnotations.initMocks(this);
   }

   @Test
   public void testDoSomething() {
      doNothing().when(amqpTemplateMock).send(anyString(), any(Message.class));

      // Call the real service class method, which internally will make 
      // use of the mock (I've verified that this works right).
      userService.doSomething(...);

      // Okay, now I need to verify that UUID string returned by 
      // "userService.doSomething(...) matches the argument that method 
      // internally passed to "amqpTemplateMock.send(...)".  Up here 
      // at the unit test level, how can I capture the arguments passed 
      // to that inject mock for comparison?
      //
      // Since the value being compared is a UUID string created 
      // internally within "userService", I cannot just verify against 
      // a fixed expected value.  The UUID will by definition always be
      // unique.
   }
}

希望此代码示例中的注释清楚地列出问题。当 Mockito 将模拟依赖项注入真实 class，并且对真实 class 进行单元测试导致它调用模拟时，您稍后如何检索传递给注入模拟的确切参数？

Answer 1

使用一个或多个 ArgumentCaptors。

不清楚你这里的类型是什么，但无论如何。让我们假设你有一个模拟，它有一个方法 doSomething() 以 Foo 作为参数，然后你这样做：

final ArgumentCaptor<Foo> captor = ArgumentCaptor.forClass(Foo.class);

verify(mock).doSomething(captor.capture());

final Foo argument = captor.getValue();

// Test the argument

此外，您的方法 returns 似乎无效，您不希望它执行任何操作。就这么写：

doNothing().when(theMock).doSomething(any());

Answer 2

您可以将 doAnswer() 挂接到 amqpTemplateMock 上的 send() 方法的存根，然后捕获 AmqpTemplate.send().

的调用参数

让你的 testDoSomething() 的第一行是这样的

    Mockito.doAnswer(new Answer<Void>() {
          @Override
          public Void answer(final InvocationOnMock invocation) {
            final Object[] args = invocation.getArguments();
            System.out.println("UUID=" + args[0]);  // do your assertions here
            return null;
          }
    }).when(amqpTemplateMock).send(Matchers.anyString(), Matchers.anyObject());

把它们放在一起，测试就变成了

import org.junit.Before;
import org.junit.Test;
import org.mockito.InjectMocks;
import org.mockito.Matchers;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.MockitoAnnotations;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;

public class UserServiceTest {

  /** This is the class whose real code I want to test */
  @InjectMocks
  private UserService userService;

  /** This is a dependency of the real class, that I wish to override with a mock */
  @Mock
  private AmqpTemplate amqpTemplateMock;

  @Before
  public void initMocks() {
    MockitoAnnotations.initMocks(this);
  }

  @Test
  public void testDoSomething() throws Exception {
    Mockito.doAnswer(new Answer<Void>() {
      @Override
      public Void answer(final InvocationOnMock invocation) {
        final Object[] args = invocation.getArguments();
        System.out.println("UUID=" + args[0]);  // do your assertions here
        return null;
      }
    }).when(amqpTemplateMock).send(Matchers.anyString(), Matchers.anyObject());
    userService.doSomething(Long.toString(System.currentTimeMillis()));
  }
}

这给出了输出

UUID=8e276a73-12fa-4a7e-a7cc-488d1ce0291f

我通过阅读这篇文章发现了这个 post， How to make mock to void methods with mockito

Mockito 如何捕获传递给注入的模拟对象方法的参数？

How can Mockito capture arguments passed to an injected mock object's methods?

java

spring

unit-testing

mockito