class UserFieldsTest

class UserFieldsTest extends KernelTestBase {
    
    /**
     * Modules to enable.
     *
     * @var array
     */
    protected static $modules = [
        'user',
        'system',
    ];
    
    /**
     * {@inheritdoc}
     */
    protected function setUp() : void {
        parent::setUp();
        $this->installEntitySchema('user');
        // Set up a test theme that prints the user's mail field.
        \Drupal::service('theme_installer')->install([
            'user_test_theme',
        ]);
        \Drupal::theme()->setActiveTheme(\Drupal::service('theme.initialization')->initTheme('user_test_theme'));
        // Clear the theme registry.
        $this->container
            ->set('theme.registry', NULL);
    }
    
    /**
     * Tests account's available fields.
     */
    public function testUserFields() {
        // Create the user to test the user fields.
        $user = User::create([
            'name' => 'foobar',
            'mail' => 'foobar@example.com',
        ]);
        $build = \Drupal::entityTypeManager()->getViewBuilder('user')
            ->view($user);
        $output = \Drupal::service('renderer')->renderRoot($build);
        $this->setRawContent($output);
        $userEmail = $user->getEmail();
        $this->assertText($userEmail, "User's mail field is found in the twig template");
    }

}