使用 Guice，如何将单元测试中的模拟对象注入到正在测试的 class 中

Question

考虑以下代码：

@Singleton
public class MyServiceImpl {
    public int doSomething() {
        return 5;
    }
}

@ImplementedBy(MyServiceImpl.class)
public interface MyService {
    public int doSomething();
}

public class MyCommand {
    @Inject private MyService service;

    public boolean executeSomething() {
        return service.doSomething() > 0;
    }
}

public class MyCommandTest {
    @InjectMocks MyServiceImpl serviceMock;
    private MyCommand command;

    @Before public void beforeEach() {
        MockitoAnnotations.initMocks(this);
        command = new MyCommand();
        when(serviceMock.doSomething()).thenReturn(-1); // <- Error here
    }

    @Test public void mockInjected() {
        boolean result = command.executeSomething();
        verify(serviceMock).doSomething();
        assertThat(result, equalTo(false));
    }
}

当我尝试在我的模拟实现对象上存根 doSomething() 方法时，我的测试失败了。我收到错误：

org.mockito.exceptions.misusing.MissingMethodInvocationException: when() requires an argument which has to be 'a method call on a mock'. For example: when(mock.getArticles()).thenReturn(articles);

Also, this error might show up because: 1. you stub either of: final/private/equals()/hashCode() methods. Those methods cannot be stubbed/verified. Mocking methods declared on non-public parent classes is not supported. 2. inside when() you don't call method on mock but on some other object.

我是通过 Guice 进行依赖注入的新手，不确定为什么我不能以这种方式模拟实现对象？

Answer 1

不使用 CDI 进行测试

一个简单的解决方案是将 CDI 与 Constructor Injection 相结合，而忽略 Guice 进行测试：

public class MyCommand {
    private final MyService service;

    @Inject
    public MyCommand(MyService service) {
        this.service = service;
    }

    public boolean executeSomething() {
        return service.doSomething() > 0;
    }
}

@RunWith(MockitoJUnitRunner.class)
public class MyCommandTest {
    @Mock
    MyServiceImpl serviceMock;
    private MyCommand command;

    @Before public void beforeEach() {
        MockitoAnnotations.initMocks(this);
        when(serviceMock.doSomething()).thenReturn(-1); // <- Error here

        // inject without Guice
        command = new MyCommand(serviceMock);
    }
}

使用 Mockito 进行 CDI 测试

否则，如果你不喜欢构造函数注入，测试代码应该是这样的：

@RunWith(MockitoJUnitRunner.class)
public class MyCommandTest {
    @Mock
    MyServiceImpl serviceMock;
    @InjectMocks 
    private MyCommand command;

    private AutoCloseable mockHandler;

    @Before
    public void beforeEach() {
        // initialize members annotated with @Mock and @InjectMocks
        mockHandler = MockitoAnnotations.openMocks(this);

        when(serviceMock.doSomething()).thenReturn(-1); // <- Error here
    }

    @After
    public void afterEach() throws Exception {
        mockHandler.close();
    }
}

使用 Guice，如何将单元测试中的模拟对象注入到正在测试的 class 中

Using Guice, how do I inject a mock object from my unit test, into the class being tested

java

dependency-injection

guice

mockito

不使用 CDI 进行测试

使用 Mockito 进行 CDI 测试