public class CustomPasswordValidator : PasswordValidator<AppUser>
    {   //override the PasswordValidator functionality with the custom definitions
        public override async Task<IdentityResult> ValidateAsync(UserManager<AppUser> manager, AppUser user, string password)
        {
            IdentityResult result = await base.ValidateAsync(manager, user, password);

            List<IdentityError> errors = result.Succeeded ? new List<IdentityError>() : result.Errors.ToList();

            //check that the username is not in the password
            if (password.ToLower().Contains(user.UserName.ToLower()))
            {
                errors.Add(new IdentityError
                {
                    Code = "PasswordContainsUserName",
                    Description = "Password cannot contain username"
                });
            }

            //check that the password doesn't contain '12345'
            if (password.Contains("12345"))
            {
                errors.Add(new IdentityError
                {
                    Code = "PasswordContainsSequence",
                    Description = "Password cannot contain numeric sequence"
                });
            }
            //return Task.FromResult(errors.Count == 0 ? IdentityResult.Success : IdentityResult.Failed(errors.ToArray()));
            return errors.Count == 0 ? IdentityResult.Success : IdentityResult.Failed(errors.ToArray());
        }
    }

//test the ability to validate new passwords with Infrastructure/CustomPasswordValidator.cs
        [Fact]
        public void Validate_Password()
        {
            //Arrange
            Mock<UserManager<AppUser>> userManager = new Mock<UserManager<AppUser>>();
            Mock<SignInManager<AppUser>> signInManager = new Mock<SignInManager<AppUser>>();
            //private UserManager<AppUser> userManager;

            Mock<AppUser> user = new Mock<AppUser>();
            //How can I assign user name/password values here?
            user.Name = "user";
            //create a password that has the username and sequence '12345' to generate errors
            user.Password = "user12345";

            //Act
            //I get an error here:
            IdentityResult result = PasswordValidator<AppUser>.ValidateAsync(userManager, user, user.Password);

            //Assert
            //demonstrate that there are two errors present
            List<IdentityError> errors = result.Succeeded ? new List<IdentityError>() : result.Errors.ToList();
            Assert.Equal(errors.Count, 2);
        }