Testing ModelState is always valid in asp.net mvc

Question

When testing my controller\'s actions the ModelState is always valid.

public class Product
{
    public int Id { get; set; }

    [Required]
    [StringLengt         


        

Answer 1

1. Create Instance of your controller class.
2. Add model state and call After adding model state

3. the modelState always give false

   controller.ModelState.AddModelError("key", "error message");
   
   var invalidStateResult = _controller.Index();
   
   Assert.IsNotNull(invalidStateResult);