我正在进行一个简单的单元测试，其中在创建课程时，“标题”字段不能为空。我必须使用具有UnitOfWork依赖注入的服务类进行测试。在调试测试时，我收到Can not instantiate proxy of class: ContosoUniversity.Models.CourseRepository异常错误。我查看了该错误，但无法理解如何修复该问题和Assert语句？
Error Message Display Image

课程存储库

public class CourseRepository : GenericRepository<Course>
{
    public CourseRepository(SchoolContext context)
        : base(context)
    {
    }

工作单位

public class UnitOfWork : IDisposable, IUnitOfWork
{
    private SchoolContext context = new SchoolContext();
    private GenericRepository<Department> departmentRepository;
    private CourseRepository courseRepository;

    public CourseRepository CourseRepository
    {
        get
        {
            if (this.courseRepository == null)
            {
                this.courseRepository = new CourseRepository(context);
            }
            return courseRepository;
        }
    }

    public virtual CourseRepository GetCourseRepository()
    {
        if (this.courseRepository == null)
        {
            this.courseRepository = new CourseRepository(context);
        }
        return courseRepository;
    }

课程服务

public class CourseService : ICourseService
{
    private IUnitOfWork unitOfWork;

    public CourseService (IUnitOfWork unitOfWork)
    {
        this.unitOfWork = unitOfWork;
    }

    public void Create(Course course)
    {
        unitOfWork.GetCourseRepository().Insert(course);
        unitOfWork.Save();
    }

    public Course GetCourseByID(int id)
    {
        return unitOfWork.GetCourseRepository().GetByID(id);
    }

测试方法

[TestMethod]
public void TestMethod1()
{
    var course = new Course
    {
        CourseID = 2210,
        Title = string.Empty,
        Credits = 3,
        DepartmentID = 1
    };

    Mock<CourseRepository> mockRepo = new Mock<CourseRepository>();
    mockRepo.Setup(m => m.GetByID(course.CourseID)).Returns(course);

    var mockUnit = new Mock<IUnitOfWork>();
    mockUnit.Setup(x => x.GetCourseRepository()).Returns(mockRepo.Object);

    var myService = new CourseService(mockUnit.Object);
    myService.Create(course);

    //var error = _modelState["Title"].Errors[0];
    //Assert.AreEqual("The Title field is required.", error.ErrorMessage);

    //mockRepo.Setup(x => x.Insert(course));
}