[英]mockito - mocking an interface - throwing NullPointerException
I am getting null pointer exception after mocking also. 我也在模拟后得到空指针异常。 Please find my project structure.
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. 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。 To test the listPets() method, I clearly knows that its using the service to get the list of pets.
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。 But my intention here to test the listPets() method of the App class, Therefore I am trying to mock the service interface.
但我的意图是在这里测试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. App类的listPets()方法使用该服务来获取宠物。 Therefore I am mocking that part using mockito.
因此,我使用mockito嘲笑那部分。
Mockito.when(petService.listPets()).thenReturn(list);
But when the unit test is running , perService.listPets() throwing NullPointerException which I have mocked using the above Mockito.when code. 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 。 Could you please help me on this?
你能帮帮我吗?
You can also use @InjectMocks
annotation, that way you wont need any getters and setters. 您也可以使用
@InjectMocks
注释,这样您就不需要任何getter和setter。 Just make sure you add below in your test case after annotating your class, 只需确保在注释课程后在测试用例中添加以下内容,
@Before
public void initMocks(){
MockitoAnnotations.initMocks(this);
}
NullPointerException is because, in App, petService isn't instantiated before trying to use it. NullPointerException是因为,在App中,petService在尝试使用之前未实例化。 To inject the mock, in App, add this method:
要在App中注入模拟,请添加以下方法:
public void setPetService(PetService petService){
this.petService = petService;
}
Then in your test, call: 然后在你的测试中,致电:
app.setPetService(petService);
before running app.listPets();
在运行
app.listPets();
之前app.listPets();
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