public async Task GetUserById()
{
var contextAccessor = Substitute.For <IHttpContextAccessor>();
var claimsFactory = Substitute.For <IUserClaimsPrincipalFactory <ApplicationUser> >();
var logger = Substitute.For <ILogger <SignInManager <ApplicationUser> > >();
var schemes = Substitute.For <IAuthenticationSchemeProvider>();
var confirmation = Substitute.For <IUserConfirmation <ApplicationUser> >();
var signInManager = Substitute.For <SignInManager <ApplicationUser> >(_userManager, contextAccessor,
claimsFactory, _optionsAccessor, logger, schemes, confirmation);
var loginValidator = new LoginValidator(signInManager, _userManager);
await loginValidator.GetUserById("admin");
await _userManager.Received().FindByNameAsync(Arg.Any <string>());
}