Mockito Spring Boot 给出空指针异常

Question

我无法在服务层为我的 Spring Boot 应用程序运行单元测试，因为它在 List<Student> expectedList = studentService.findAl(); 行给了我空指针异常。但是，如果我直接调用模拟，它可以工作List<Student> expectedList = studentRepository.findAll();。 studentRepository 被注入到 studentService 中。谁能说明问题是什么？
测试类：

import com.demo.student.demo.entity.Student;
import com.demo.student.demo.repository.StudentRepository;
import org.junit.jupiter.api.Test;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import static org.mockito.Mockito.*;

import java.util.ArrayList;
import java.util.List;

import static org.junit.jupiter.api.Assertions.*;

public class StudentServiceImplTest {

    @Mock
    private StudentRepository studentRepository;

    @InjectMocks
    private StudentServiceImpl studentService;

    @Test
    public void findAll(){
        List<Student> studentList = new ArrayList<>();
        studentList.add(new Student(1, "person1", "person1@mail.com"));
        studentList.add(new Student(2, "person2", "person2@mail.com"));

        when(studentRepository.findAll()).thenReturn(studentList);

        List<Student> expectedList = studentService.findAl();

        assertEquals(0, expectedList.size());
    }


}

和存储库：

@Repository
public interface StudentRepository extends JpaRepository<Student, Long> {
}

服务接口：

public interface StudentService {

    public List<Student> findAl();
    public Student findById(long id);
    public Student saveOrUpdate(Student student);
    public void deleteById(long id);

}

以及服务实现：

@Service
public class StudentServiceImpl implements StudentService {

    @Autowired
    private StudentRepository studentRepository;

    @Override
    public List<Student> findAl() {
        return studentRepository.findAll();
    }

    @Override
    public Student findById(long id) {
        Optional<Student> student = studentRepository.findById(id);
        boolean exist = student.isPresent();
        return exist? student.get() : null;
    }

    @Override
    public Student saveOrUpdate(Student student) {
        studentRepository.save(student);
        return student;
    }

    @Override
    public void deleteById(long id) {
        studentRepository.deleteById(id);
    }

}

Answer 1

我对您的代码做了一些修改。 我所做的更改是在 StudentServiceImpl 类中。我删除了@Autowired 注释并进行了构造函数注入。

@Service
public class StudentServiceImpl implements StudentService {

private final StudentRepository studentRepository;

public StudentServiceImpl(StudentRepository studentRepository) {
    this.studentRepository = studentRepository;
}

//others are same
}

在测试类中。

@RunWith(MockitoJUnitRunner.class)
public class StudentServiceImplTest {

private StudentService studentService;
private StudentRepository studentRepository;

@Test
public void findAll(){
    studentRepository = mock(StudentRepository.class);
    studentService = new StudentServiceImpl(studentRepository);
    List<Student> studentList = new ArrayList<>();
    studentList.add(new Student(1, "person1", "person1@mail.com"));
    studentList.add(new Student(2, "person2", "person2@mail.com"));

    when(studentRepository.findAll()).thenReturn(studentList);

    List<Student> expectedList = studentService.findAl();

    assertEquals(2, expectedList.size());
 }
}

现在我可以看到测试通过了。

另外，请阅读此 article，上面写着“摆脱 @InjectMocks”。

希望对你有帮助 :) 非常感谢。

Answer 2

您在此处配置的模拟：

    StudentRepository studentRepository = mock(StudentRepository.class);

没有注入到服务中。在你的测试中删除 studentRepository 的初始化，只使用你已经用 @Mock 注释的那个。