public void DeleteOrderValidationTest(int?id)
{
//Arrange
var mockUow = new Mock <IUnitOfWork>();
mockUow.Setup(a => a.Orders.Get(-1)).Returns((Order)null);
//Act
var service = new RentService(mockUow.Object);
//Assert
Assert.Throws <ValidationException>(
() =>
service.DeleteOrder(id));
}