为什么 Java Spring 中的 @InjectMocks 在我的服务测试用例中返回 null？

Question

我正在尝试为我在 Spring 中为控制器实现的服务编写测试用例。我有以下服务和测试课程。

学生课程请求服务：

import java.util.List;
import org.springframework.stereotype.Service;
import model.CourseRequest;
import repository.ICourseRequestRepository;
import lombok.RequiredArgsConstructor;

@Service
@RequiredArgsConstructor
public class StudentCourseRequestService implements IStudentCourseRequestService {

    private final ICourseRequestRepository courseRequestRepository;

    @Override
    public boolean requestCourse(CourseRequest courseRequest) {
        return courseRequestRepository.saveRequest(courseRequest);
    }

    @Override
    public List<CourseRequest> getAllCourseRequests() {
        return courseRequestRepository.getAllCourseRequests();
    }

    @Override
    public List<CourseRequest> getAllCourseRequestsOfStudent(Long studentId) {
        return courseRequestRepository.getCourseRequestsByStudentId(studentId);
    }
    
}

测试班：

import org.junit.jupiter.api.Test;
import org.mockito.InjectMocks;
import org.mockito.Mockito;
import org.springframework.boot.test.mock.mockito.MockBean;
import static org.assertj.core.api.Assertions.assertThat;
import model.CourseRequest;
import repository.ICourseRequestRepository;

public class StudentCourseRequestServiceTests {
    @MockBean
    private ICourseRequestRepository courseRequestRepository;

    @InjectMocks
    private StudentCourseRequestService studentCourseRequestService;

    @Test
    public void requestValidCourse() throws Exception {
        final CourseRequest courseRequest = new CourseRequest(
            "data0",
            "data1",
            "data2",
            "data3",
            "data4",
            "data5"
        );

        Mockito.when(courseRequestRepository.saveRequest(courseRequest)).thenReturn(true);
        boolean result = studentCourseRequestService.requestCourse(courseRequest);
        assertThat(result).isTrue();
    }
}

当我运行

requestValidCourse()

测试用例时，出现以下错误：

java.lang.NullPointerException: Cannot invoke "repository.ICourseRequestRepository.saveRequest(model.CourseRequest)" because "this.courseRequestRepository" is null
 at service.StudentCourseRequestServiceTests.requestValidCourse(StudentCourseRequestServiceTests.java:29)
 at java.base/java.util.ArrayList.forEach(Unknown Source)
 at java.base/java.util.ArrayList.forEach(Unknown Source)

如何解决这个问题？

Answer 1

按照 @Lesiak 的建议，我将

@ExtendWith(MockitoExtension.class)

注释添加到类的顶部，并将

courseRequestRepository

更改为具有

@Mock

注释，而不是之前的

@MockBean

注释。这些更改后问题得到解决。

之前，我在试验期间使用了 @Lesiak 推荐的配置来解决该问题，但我还在类的顶部添加了注释

@ExtendWith(SpringExtension.class)

。使用此配置，我遇到了同样的错误。删除

@ExtendWith(SpringExtension.class)

注释解决了这里的问题。

新测试班：

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.junit.jupiter.MockitoExtension;
import static org.assertj.core.api.Assertions.assertThat;
import model.CourseRequest;
import repository.ICourseRequestRepository;

@ExtendWith(MockitoExtension.class)
public class StudentCourseRequestServiceTests {
    @Mock
    private ICourseRequestRepository courseRequestRepository;

    @InjectMocks
    private StudentCourseRequestService studentCourseRequestService;

    @Test
    public void requestValidCourse() throws Exception {
        final CourseRequest courseRequest = new CourseRequest(
        "data0",
        "data1",
        "data2",
        "data3",
        "data4",
        "data5"
    );

        Mockito.when(courseRequestRepository.saveRequest(courseRequest)).thenReturn(true);
        boolean result = studentCourseRequestService.requestCourse(courseRequest);
        assertThat(result).isTrue();
    }
}

Answer 2

请注意以下几点：

1. 你在使用

   @org.mockito.InjectMocks

   吗？

2. JUnit版本： 2.1）如果是JUnit 4，则配置测试类如下：

   @org.junit.Before
   public void setUp() {
       org.mockito.MockitoAnnotations.openMocks(this);
   }
   

   2.2) 如果是 JUnit 5：

   @org.junit.BeforeEach
   void setUp() {
       MockitoAnnotations.openMocks(this);
   }
   

3. 就我而言，我在课堂上没有使用

   @ExtendWith(MockitoExtension.class)

   。