Mockito将模拟注入Spy对象

Question

我正在为一个具有2级依赖注入的类编写测试用例.我使用@Spy注释作为1级依赖注入对象,我想模拟第二级注入.但是,我一直在第二级获得空指针异常.有没有办法将模拟注入@Spy对象？

public class CarTestCase{
    @Mock
    private Configuration configuration;

    @Spy 
    private Engine engine;

    @InjectMocks 
    private Car car;

    @Test
    public void test(){

       Mockito.when(configuration.getProperties("")).return("Something");
       car.drive();
    }

}

public class Car{
    @Inject
    private Engine engine;

    public void drive(){
        engine.start();
    }
}

public class Engine{
    @Inject 
    private Configuration configuration;

    public void start(){
        configuration.getProperties();   // null pointer exception
    }

}

Answer 1

我也徘徊如何将模拟注入间谍.

下面的方法将无法正常工作:

@Spy
@InjectMocks
private MySpy spy;

但是,当使用注释和手动模拟时,可以通过"混合"方法实现期望的行为.以下工作完美:

@Mock
private NeedToBeMocked needToBeMocked;

@InjectMocks
private MySpy mySpy;

@InjectMocks
private SubjectUnderTest sut;

@BeforeMethod
public void setUp() {
    mySpy = Mockito.spy(new MySpy());
    MockitoAnnotations.initMocks(this);
}

(SubjectUnderTest这取决于MySpy,并MySpy依次NeedToBeMocked).

UPD:就个人而言,我认为如果你不得不经常做这样的魔术,这可能表明你的类之间的依赖关系有问题,并且值得进行一些重构来改进你的代码.

Answer 2

对我有用的（最简单的）解决方案。

@InjectMocks
private MySpy spy = Mockito.spy(new MySpy());

MockitoAnnotations.initMocks(this)在这种情况下不需要，只要测试类用@RunWith(MockitoJUnitRunner.class).

Answer 3

Mockito不能进行如此棘手的注射,因为它不是注射框架.因此,您需要重构代码以使其更易于测试.使用构造函数注入很容易完成:

public class Engine{
    private Configuration configuration;

    @Inject 
    public Engine(Configuration configuration) {
        this.configuration = configuration;
    }
    ........
}

public class Car{
    private Engine engine;

    @Inject    
    public Car(Engine engine) {
        this.engine = engine;
    }
}

在这种情况下,您必须手动处理模拟和注入:

public class CarTestCase{

    private Configuration configuration;

    private Engine engine;

    private Car car;

    @Before
    public void setUp(){
        configuration = mock(Configuration.class);
        engine = spy(new Engine(configuration));
        car = new Car(engine);
    }

    @Test
    public void test(){

       Mockito.when(configuration.getProperties("")).return("Something");
       car.drive();
    }

}

Answer 4

我在使用Spring启动框架进行单元测试期间也遇到了这个问题,但我找到了一个使用@Spy和@InjectMocks的解决方案

以前的回答来自Yoory N.

@Spy
@InjectMocks
private MySpy spy;

因为InjectMocks需要创建实例,所以适合我的解决方案在下面,

@Spy
@InjectMocks
private MySpy spy = new MySpy();