Java mockito - 模拟接口 - 抛出 NullPointerException
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mockito - mocking an interface - throwing NullPointerException
提问by Arun K
I am getting null pointer exception after mocking also. Please find my project structure.
我也在模拟后得到空指针异常。请找到我的项目结构。
//this is the pet interface
public interface Pet{
}
// An implementation of Pet
public class Dog extends Pet{
int id,
int petName;
}
// This is the Service Interface
public interface PetService {
List<Pet> listPets();
}
// a client code using the PetService to list Pets
public class App {
PetService petService;
public void listPets() {
// TODO Auto-generated method stub
List<Pet> listPets = petService.listPets();
for (Pet pet : listPets) {
System.out.println(pet);
}
}
}
// This is a unit test class using mockito
public class AppTest extends TestCase {
App app = new App();
PetService petService = Mockito.mock(PetService.class);
public void testListPets(){
//List<Pet> listPets = app.listPets();
Pet[] pet = new Dog[]{new Dog(1,"puppy")};
List<Pet> list = Arrays.asList(pet);
Mockito.when(petService.listPets()).thenReturn(list);
app.listPets();
}
}
I am trying to use TDD here, Means I have the service interface written, But not the actual implementation. To test the listPets() method, I clearly knows that its using the service to get the list of pets. But my intention here to test the listPets() method of the App class, Therefore I am trying to mock the service interface.
我在这里尝试使用 TDD，意味着我已经编写了服务接口，但不是实际的实现。为了测试 listPets() 方法，我清楚地知道它使用该服务来获取宠物列表。但是我在这里打算测试 App 类的 listPets() 方法，因此我试图模拟服务接口。
The listPets() method of the App class using the service to get the pets. Therefore I am mocking that part using mockito.
使用服务获取宠物的 App 类的 listPets() 方法。因此，我正在使用 mockito 来嘲笑那部分。
Mockito.when(petService.listPets()).thenReturn(list);
But when the unit test is running , perService.listPets() throwing NullPointerExceptionwhich I have mocked using the above Mockito.whencode. Could you please help me on this?
但是当单元测试运行时， perService.listPets() 抛出NullPointerException我已经使用上面的Mockito.when代码进行了模拟。你能帮我解决这个问题吗？
采纳答案by Chris
NullPointerException is because, in App, petService isn't instantiated before trying to use it. To inject the mock, in App, add this method:
NullPointerException 是因为，在 App 中，petService 在尝试使用之前没有被实例化。要注入模拟，请在 App 中添加此方法：
public void setPetService(PetService petService){
this.petService = petService;
}
Then in your test, call:
然后在您的测试中，调用：
app.setPetService(petService);
before running app.listPets();
跑步前 app.listPets();
回答by Srinivas Pasupulate
You can also use @InjectMocksannotation, that way you wont need any getters and setters. Just make sure you add below in your test case after annotating your class,
您还可以使用@InjectMocks注释，这样您就不需要任何 getter 和 setter。只需确保在对类进行注释后在测试用例中添加以下内容，
@Before
public void initMocks(){
MockitoAnnotations.initMocks(this);
}
