单元测试中的对象引用错误

Question

我有一个控制器操作

  [HttpPost]
   public ActionResult CreateFocus(FocusFormModel focus)
    {
        var errors = focusService.CanAddFocus(Mapper.Map<FocusFormModel, Focus>(focus)).ToList();
        ModelState.AddModelErrors(errors);
        if (ModelState.IsValid)
        {
            focusService.CreateFocus(Mapper.Map<FocusFormModel, Focus>(focus));
            var createdfocus = focusService.GetFocus(focus.FocusName);
            return RedirectToAction("Focus", new { id = createdfocus.FocusId });
        }
        return View("CreateFocus", focus);
    }

此操作工作正常，但是当我编写单元测试时，它显示错误

对象引用 未设置为对象的实例

UNI 测试是

 [Test]
    public void Create_Focus()
    {
        // Arrange                    
        GroupController controller = new GroupController(groupService);
        // Act

        FocusFormModel focus = new FocusFormModel();
           focus.GroupId  = 1;
            focus.FocusName = "t";
            focus.Description = "t";
        Mapper.CreateMap<FocusFormModel, Focus>().ForAllMembers(opt => opt.Ignore());
        Mapper.AssertConfigurationIsValid();
        var result = (RedirectToRouteResult)controller.CreateFocus(focus);
          Assert.AreEqual("Index", result.RouteValues["action"]);
     }

我的模型描述如下

public class Focus
{
    public int FocusId { get; set; }
    [StringLength(50)]
    public string FocusName { get; set; }
    [StringLength(100)]
    public string Description { get; set; }
    public int GroupId { get; set; }
    public virtual Group Group { get; set; }
    public DateTime CreatedDate { get; set; }

    public Focus()
    {
        CreatedDate = DateTime.Now;
    }
}

我正在编写我的视图模型

public class FocusFormModel
{
    public int FocusId { get; set; }
    [Required(ErrorMessage = "*")]
    [StringLength(50)]
    public string FocusName { get; set; }
    [Required(ErrorMessage = "*")]
    [StringLength(100)]
    public string Description { get; set; }
    public int GroupId { get; set; }
    public virtual Group Group { get; set; }
    public DateTime CreatedDate { get; set; }
    public FocusFormModel()
    {
        CreatedDate = DateTime.Now;
    }
}

任何人都可以帮我吗

Answer 1

这一行实际上提供了 2 次获得空引用异常的机会：

var errors = focusService.CanAddFocus(Mapper.Map<FocusFormModel, Focus>(focus)).ToList();

首先，focusService可能是null

如果 focusService 不为 null，则方法调用CanAddFocus(Mapper.Map<FocusFormModel, Focus>(focus))可能会返回null

这只是假设。
正如 Greg Smith 所说，堆栈跟踪在这里会非常有帮助。