XUnit 测试，检查异常

告诉我如何确保在检查异常时测试不落空ObjectNotFoundError

我模拟了一项服务，在设置中我尝试实现抛出异常的模拟

public async Task GetRequestWithNoSucccessNotFound()
{
    var mockService = new Mock<ICompanyService>();
    var mockLogger = new Mock<ILogger<CompaniesController>>();
    mockService.Setup(service => service.GetCompany(It.IsAny<int>())).Throws<ObjectNotFoundException>();
    var controller = new CompaniesController(mockLogger.Object, mockService.Object);

    var result = await controller.Get(9999);

    var viewResult = Assert.IsType<RequestResponseModel<CompanyViewModel>>(result);
    Assert.False(result.IsSuccess);
}

服务方法如下所示

public async Task<CompanyViewModel> GetCompany(int companyId)
{
    var company = await contextDb.Companies.AsNoTracking().Where(p => p.Id == companyId).SelectCompany().FirstOrDefaultAsync();
    if (company == null)
    {
        throw new ObjectNotFoundException();
    }
    return company;
}

在这种情况下，测试失败并出现错误

System.NullReferenceException : Object reference not set to an instance of an object.

我怎样才能让假对象不放弃测试，但抛出一个在控制器中处理的异常？

UPD

得到

public async Task<RequestResponseModel<CompanyViewModel>> Get(int id)
{
    try
    {
        var company = await CompanyService.GetCompany(id);
        return RequestResponseModel<CompanyViewModel>.CreateSuccessObject(company);
    }
    catch (Exception e)
    {
        LogError(e);
        this.SetErrorResponseStatusCode(e);
        return RequestResponseModel<CompanyViewModel>.CreateRequestResponseErrorObject();
    }
}

SetErrorResponseStatusCode

public static void SetErrorResponseStatusCode(this ControllerBase controller, Exception exception)
    {
        // set http status based on type of exception
        if (exception is NotImplementedException)
        {
            controller.Response.StatusCode = (int)HttpStatusCode.NotImplemented;
        }
        else if (exception is ObjectNotFoundException)
        {
            controller.Response.StatusCode = (int)HttpStatusCode.NotFound; // вот здесь падает
        }
        else
        {
            controller.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
        }
    }

我想指出，只有测试下降。访问 API 时，一切正常。