visit() and see() and all that not working

I decided to start doing tests to make my life easier, but I'm having one problem: Stuff like

$this->visit("/")->see("Laravel 5")

is not working. This is the error I get:

PHPUnit 4.6.6 by Sebastian Bergmann and contributors.

Configuration read from /var/www/booksite/phpunit.xml

PHP Fatal error:  Call to undefined method AuthTest::visit() in /var/www/booksite/tests/AuthTest.php on line 15
                                                      [Symfony\Component\Debug\Exception\FatalErrorException]   
Call to undefined method AuthTest::visit()            

My test:

<?php

use Illuminate\Foundation\Testing\WithoutMiddleware;
use Illuminate\Foundation\Testing\DatabaseTransactions;

class AuthTest extends TestCase
{
    /**
     * A basic functional test example.
     *
     * @return void
     */
    public function testBasicExample()
    {
        $this->visit('/')
            ->see('Laravel 5');
    }
}

(The name AuthTest is for something else, I just want to get this working.)

Any idea what's going on?