Mockito @InjectMocks 如何工作

Question

从这个Difference between @Mock and @InjectMocks我了解到@InjectMocks被用作注解创建一个实例并将使用 @Mock 创建的模拟注入其中。我不认为我理解它是如何工作的。

我有一个示例代码，我想问你 2 个问题，以便直接进入我不清楚的地方。问题在最后。

我有一个界面：

public interface SimpleAgenda {

    public List<String> getAppointments();

    public String getAppointment(Date d);

    public void addAppointments(Date d, String label);

}

和实现此接口的class：

public class MyAgenda implements SimpleAgenda {

    private Map<String, String> appointments;

    @Override
    public List<String> getAppointments() {
        List<String> lst = new ArrayList<String>();
        System.out.println(this.appointments == null);
        for (String key : this.appointments.keySet()) {
            String label = this.appointments.get(key);
            lst.add(label);
        }

        return lst;
    }

    @Override
    public String getAppointment(Date d) {
        String dateString = d.toString();
        String app = this.appointments.get(dateString);
        
        return app;
    }

    @Override
    public void addAppointments(Date d, String label) {
        // TODO Auto-generated method stub
        // this behavior is not implemented yet in this class
    }

}

终于有考试了 class:

// @RunWith attaches a runner with the test class to initialize the test data
@RunWith(MockitoJUnitRunner.class)
public class AgendaTest {

    private static final String LABEL = "This is a mock appointment for: ";

    // @InjectMocks annotation is used to create and inject the mock object
    @InjectMocks
    MyAgenda agenda = new MyAgenda();

    // @Mock annotation is used to create the mock object to be injected
    @Mock
    Map<String, String> mockedAppointments;

    @Before
    public void createMocks() {
        Date d1 = (new GregorianCalendar(120, 4, 15)).getTime();
        Date d2 = (new GregorianCalendar(119, 7, 31)).getTime();

        String key;

        key = d1.toString();
        // add the mocked behavior of for a set of given dates
        when(mockedAppointments.get(key)).thenReturn(LABEL + key);

        key = d2.toString();
        // 1. add the mocked behavior of for a set of given dates.
        // 2. Strict stubbing that requires that all declared stubs are actually used
        //    the statement lenient() relax this requirement. Check the manual. 
        lenient().when(mockedAppointments.get(key)).thenReturn(LABEL + key);

        when(mockedAppointments.size()).thenReturn(2);
    }

    @Test
    public void mockTest() {
        for (String key : mockedAppointments.keySet()) {
            String v = mockedAppointments.get(key);
// Do not worry, we will never reach this line. We are querying the object on 
// method that was not mocked (i.e. keySet).            
            Assert.fail();
        }

        int size = mockedAppointments.size();

        Assert.assertEquals(2, size);
    }

    @Test
    public void simpleTest() {
        int appCounter = agenda.getAppointments().size();
// Do not expect that appCounter is 2 (or more in general different than 0) ... 
// we are actually querying an object that was not mocked!!!
// See the details of the implementation of the method: MyAgenda.getAppointments()
        Assert.assertEquals(0, appCounter);
    }

这些是我的问题：

在 mockTest() 中，当我调用 mockedAppointments.keySet() 时，它 return 是一个空集...我的问题是：为什么 mockedAppointments.keySet() 不抛出 nullPointerException（mockedAppointments 仅声明）？也许是因为它是一个模拟？如果是这个原因，为什么模拟不抛出“nullPointerException”？
在simpleTest()中我们有agenda.getAppointments().size();； agenda.getAppointments() 包含 System.out.println(this.appointments == null); 并且此行打印“false”是我保留@InjectMocks 注释，否则为“true”，但为什么呢？在第一种情况下（保留@InjectMocks）“agenda”的“appointments”属性在哪里初始化？是不是因为我们把mockedAppointments的值注入进去才初始化的？如果是，Mockito 是否仅根据测试 class 中定义的 mock 类型和 MyAgenda 中定义的属性类型来执行此操作？

Answer 1

问为什么 mockedAppointments.keySet() 不抛出 nullPointerException（仅声明了 mockedAppointments）？也许是因为它是一个模拟？如果是这个原因，为什么模拟不抛出“nullPointerException”？
答案是：因为 mockedAppointments.keySet().size 是 0 而 mockedAppointments.keySet() 是空的，所以这是 mock
2.0 Qn System.out.println(this.appointments == null);行打印“false”是我保留@InjectMocks 注释，否则为“true”，但为什么呢？
答案是：在 junit 或 mockito 中 System.out.println 不起作用，而是使用记录器。
2.1 Qn 第一种情况（保留@InjectMocks）“agenda”的“appointments”属性在哪里初始化？
答案是：它正在模拟 class，例如，对于列表，它初始化为 0 并将值保持为空，除此之外

@InjectMocks
private MyAgenda agenda;

应该这样声明
2.2 Qn是不是因为我们给它注入了mockedAppointments的值，所以初始化了？
答案是：mockedAppointments 和 agenda 没有任何联系，除此之外相反，你可以使用这个 injectMocks @Mocks，它有效。

 @Mocks
 private MyAgenda agenda;

Mockito @InjectMocks 如何工作

Mockito how does @InjectMocks works

java

junit

mockito