Code snippet that can be used to Log in user programmatically in Drupal 8.
use Drupal\user\Entity\User;
use Symfony\Component\HttpFoundation\RedirectResponse;
$user = User::create([
'name' => $userEmail,
'mail' => $userEmail,
'pass' => $password,
'status' => 1,
]);
user_login_finalize($user);
$user_destination = \Drupal::destination()->get();
$response = new RedirectResponse($user_destination);
$response->send();
