Java 用Mockito和Spring Boot进行深度模拟

我需要（用Mockito）模拟“B”类使用的“A”类，但是我的测试用例是针对“D”类的

参见我的示例：

@Service
public class Aclass {
    public Long sumTwoNumbers(Long a, Long b){
       return a + b;
    }
}

@Service
public class Bclass {
     @Autowired    
     private  Aclass classA;

     public Long sunThreeNumbers(Long a, Long b, Long c){
           return classA.sumTwoNumbers(a, b) + c;
     }
}

@Service
public class Cclass {
     @Autowired    
     private  Bclass classB;

     public Long sunFourNumbers(Long a, Long b, Long c, Long d){
           return classB.sunThreeNumbers(a, b, c) + d;
     }
}

@Service
public class Dclass {
     @Autowired    
     private  Cclass classC;

     public Long sunFourNumbers(Long a, Long b, Long c, Long d){
           return classC.sunFourNumbers(a, b, c, d);
     }
}

我的测试是：

@ExtendWith(MockitoExtension.class)
public class DclassTest{

     @InjectMocks    
     private  Dclass classD;

     @Mock    
     private  Aclass classA; 
     /* Look , I need to mock Aclass , not Bclass or Cclass. */
     
     @Test
     public void testSunFourNumbers(){
        Mockito.when(classA.sumTwoNumbers(any(Long.class), any(Long.class))).thenReturn(0L);

        Long sum = classC.sunFourNumbers(1L, 1L, 1L, 1L);

        Assert.assertEquals(2L, sum);        
     } 
}

这是我所需要的一个简单的例子

当我运行这个时，我在Dclass中收到了NullPointerException

---

有可能吗？

我认为您应该用Mockito测试您的类B类，如下所示：

public class BclassTest {

        Long a = 0L;
        Long b = 0L;
        Long c = 1L;
         
         @InjectMocks
         private Bclass bclass;

         @Mock
         private Aclass aclass;
       
         //You Should initialize your Mock Objects in @Before method.
         @Before
         public void setup() {
         MockitoAnnotations.initMocks(this);

         @Test
         public void testSunThreeNumbers(){             
         Mockito.when(aclass.sumTwoNumbers(anyLong(),anyLong())).thenReturn(0L);
         assertEquals(Long.valueOf(1), bclass.sunThreeNumbers(Long a, Long b, Long c));
                }
         }
       }

---

我认为你应该用Mockito测试你的类B类，如下所示：

public class BclassTest {

        Long a = 0L;
        Long b = 0L;
        Long c = 1L;
         
         @InjectMocks
         private Bclass bclass;

         @Mock
         private Aclass aclass;
       
         //You Should initialize your Mock Objects in @Before method.
         @Before
         public void setup() {
         MockitoAnnotations.initMocks(this);

         @Test
         public void testSunThreeNumbers(){             
         Mockito.when(aclass.sumTwoNumbers(anyLong(),anyLong())).thenReturn(0L);
         assertEquals(Long.valueOf(1), bclass.sunThreeNumbers(Long a, Long b, Long c));
                }
         }
       }

---

根据示例代码，很明显，下面的服务依赖如下

DClass依赖于Cclass

B类上的C类和

A类上的B类

当我们为Dclass编写单元测试用例时（代码如下所示）

这里，Dclass直接依赖于Cclass，所以在这种情况下，模拟Cclass就足够了。单元测试就是通过模拟一个小单元的直接依赖项来测试它

 @InjectMocks Dclass classD; // It has all 3 mocks now (but A and B mocks not needed)
 @Mock Aclass classA;        //not needed (Dclass not dependent on Aclass)
 @Mock Bclass classB;        //not needed (Dclass not dependent on Bclass)    
 @Mock Cclass classC;        // **Mandatory** - Because Dclass is directly dependent on Cclass
 
 As per your code - you have a mock for Aclass and injected mock into Dclass.
 When(...).then(...) written for Aclass mock.

 @Test
 public void testSunFourNumbers(){

    Mockito.when(classA.sumTwoNumbers(any(Long.class), any(Long.class))).thenReturn(0L);

    //Since you don't have mock for 'classC' in your code, it will go as null and result in nullpointer
    Long sum = classC.sunFourNumbers(1L, 1L, 1L, 1L);

    Assert.assertEquals(2L, sum);        
 }         

---

根据示例代码，很明显，下面的服务依赖如下

DClass依赖于Cclass

B类上的C类和

A类上的B类

当我们为Dclass编写单元测试用例时（代码如下所示）

这里，Dclass直接依赖于Cclass，所以在这种情况下，模拟Cclass就足够了。单元测试就是通过模拟一个小单元的直接依赖项来测试它

 @InjectMocks Dclass classD; // It has all 3 mocks now (but A and B mocks not needed)
 @Mock Aclass classA;        //not needed (Dclass not dependent on Aclass)
 @Mock Bclass classB;        //not needed (Dclass not dependent on Bclass)    
 @Mock Cclass classC;        // **Mandatory** - Because Dclass is directly dependent on Cclass
 
 As per your code - you have a mock for Aclass and injected mock into Dclass.
 When(...).then(...) written for Aclass mock.

 @Test
 public void testSunFourNumbers(){

    Mockito.when(classA.sumTwoNumbers(any(Long.class), any(Long.class))).thenReturn(0L);

    //Since you don't have mock for 'classC' in your code, it will go as null and result in nullpointer
    Long sum = classC.sunFourNumbers(1L, 1L, 1L, 1L);

    Assert.assertEquals(2L, sum);        
 }         

---

不清楚当

Dclass

取决于

Cclass

时，为什么要模拟

Aclass

，是否愿意解释您的推理？不清楚当

Dclass

取决于

Cclass

时，为什么要模拟

Aclass

，是否愿意解释您的推理？