Mockito

1、添加依赖

<dependency>
  <groupId>org.mockito</groupId>
  <artifactId>mockito-all</artifactId>
  <scope>test</scope>
</dependency>

2、开启Mock

2.1 Mockito.mock

直接使用Mockito提供的mock方法即可以模拟出一个服务的实例。

public class MockitoAnnotationTest {
    @Test
    public void whenNotUseMockAnnotation_thenCorrect() {
        //mock creation
        List mockedList = Mockito.mock(List.class);
  }
}

2.2 MockitoAnnotations.initMocks(this)

这里给出了使用@Mock注解来Mock对象时的第一种实现，即使用MockitoAnnotations.initMocks(testClass)。

public class MockitoAnnotationTest {
    @Mock
    List<String> mockedList;
  @Before
  public void before() {
      //MockitoAnnotations.initMocks(this); //initMocks方法已过时
        MockitoAnnotations.openMocks(this);
  }
    @Test
    public void whenUseMockAnnotation_thenMockIsInjected() {
        mockedList.add("one");
    }
}

2.3 @RunWith(MockitoJUnitRunner.class)

在测试用例上带上了这个注解后，就可以自由的使用@Mock来Mock对象啦。

@RunWith(MockitoJUnitRunner.class)  
public class MockitoAnnotationTest {
  @Mock
    List<String> mockedList;
    @Test
    public void whenUseMockAnnotation_thenMockIsInjected() {
        mockedList.add("one");
    }
}

2.4 MockitoRule

这里需要注意的是如果使用MockitoRule的话，该对象的访问级别必须为public。

public class MockitoAnnotationTest {
    @Rule
    public MockitoRule initRule = MockitoJUnit.rule();
  @Mock
    List<String> mockedList;
    @Test
    public void whenUseMockAnnotation_thenMockIsInjected() {
        mockedList.add("one");
    }
}

在上面四种方法中，最推荐的就是第二种方法，如果无法使用@RunWith(MockitoJUnitRunner.class)时，再考虑别的兼容的方法。

3、verify

一旦mock对象被创建了，mock对象会记住所有的交互。然后你就可能选择性的验证你感兴趣的交互。

// 静态导入会使代码更简洁
import static org.mockito.Mockito.*;
// mock creation 创建mock对象
List mockedList = mock(List.class);
//using mock object 使用mock对象
mockedList.add("one");
mockedList.clear();
verify(mockedList).add("one");
verify(mockedList).clear();

4、测试桩

LinkedList mockedList = mock(LinkedList.class);
 //stubbing
 when(mockedList.get(0)).thenReturn("first");
 when(mockedList.get(1)).thenThrow(new RuntimeException());
 //following prints "first"
 System.out.println(mockedList.get(0));
 //following throws runtime exception
 System.out.println(mockedList.get(1));
 //following prints "null" because get(999) was not stubbed
 System.out.println(mockedList.get(999));
 verify(mockedList).get(0);
doThrow(new RuntimeException()).when(mockedList).clear();
//following throws RuntimeException:
mockedList.clear();

5、参数匹配器

Mockito以自然的java风格来验证参数值: 使用equals()函数。有时，当需要额外的灵活性时你可能需要使用参数匹配器，也就是argument matchers :

//stubbing using built-in anyInt() argument matcher
 when(mockedList.get(anyInt())).thenReturn("element");
 //stubbing using custom matcher (let's say isValid() returns your own matcher implementation):
 when(mockedList.contains(argThat(isValid()))).thenReturn("element");
 //following prints "element"
 System.out.println(mockedList.get(999));
 //you can also verify using an argument matcher
 verify(mockedList).get(anyInt());

6、验证调用次数

//using mock
 mockedList.add("once");
 mockedList.add("twice");
 mockedList.add("twice");
 mockedList.add("three times");
 mockedList.add("three times");
 mockedList.add("three times");
 //following two verifications work exactly the same - times(1) is used by default
 verify(mockedList).add("once");
 verify(mockedList, times(1)).add("once");
 //exact number of invocations verification
 verify(mockedList, times(2)).add("twice");
 verify(mockedList, times(3)).add("three times");
 //verification using never(). never() is an alias to times(0)
 verify(mockedList, never()).add("never happened");
 //verification using atLeast()/atMost()
 verify(mockedList, atMostOnce()).add("once");
 verify(mockedList, atLeastOnce()).add("three times");
 verify(mockedList, atLeast(2)).add("three times");
 verify(mockedList, atMost(5)).add("three times");
//verify that method was never called on a mock
 verify(mockOne, never()).add("never");

参考资料：

• https://cloud.tencent.com/developer/article/1516985