@RunWith(SpringRunner.class)
@SpringBootTest
public class ApplicationTests {
    // ...
    
    private Student insertStudent(String name, int grade) {
        Student s = new Student();
        s.setName(name);
        s.setGrade(grade);
        studentRepository.save(s);
        return studentRepository.findById(s.getId()).orElseThrow();
    }

    private Course insertCourse(String name, int credit) {
        Course c = new Course();
        c.setName(name);
        c.setCredit(credit);
        courseRepository.save(c);
        return courseRepository.findById(c.getId()).orElseThrow();
    }

    private Department insertDepartment(String name) {
        Department d = new Department();
        d.setName(name);
        departmentRepository.save(d);
        return departmentRepository.findById(d.getId()).orElseThrow();
    }
}