問題描述

我正在為具有 2 級依賴注入的類編寫測試用例.我對 1 級依賴注入對象使用 @Spy 注釋，我想模擬第 2 級注入.但是，我在第二級不斷收到空指針異常.有什么方法可以將模擬注入@Spy 對象?

I'm writing a test case for a Class which has a 2 level of dependency injection. I use @Spy annotation for the 1 level dependency injection object, and I would like to Mock the 2nd level of injection. However, I kept getting null pointer exception on the 2nd level. Is there any way that I inject the mock into the @Spy object?

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
    }

}

推薦答案

Mockito 不能執(zhí)行如此棘手的注入，因為它不是一個注入框架.因此，您需要重構(gòu)代碼以使其更具可測試性.使用構(gòu)造函數(shù)注入很容易做到:

Mockito cannot perform such a tricky injections as it's not an injection framework. So, you need to refactor your code to make it more testable. It's easy done by using constructor injection:

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;
    }
}

在這種情況下，您必須手動處理模擬和注入:

In this case you have to handle the mocking and injection manually:

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();
    }

}

這篇關(guān)于Mockito 將模擬注入 Spy 對象的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！