Class WebTestCase not found when checking debug:wiring

When checking php bin/console debug:wiring, I get the following errors:

In FileLoader.php line 168:

  Class Symfony\Bundle\FrameworkBundle\Test\WebTestCase not found in /vagrant/mysymfony/app/config/services.yml (whic
  h is being imported from "/vagrant/mysymfony/app/config/config.yml").


In WebTestCase.php line 17:

  Class Symfony\Bundle\FrameworkBundle\Test\WebTestCase not found


In WebTestCase.php line 21:

  Class Symfony\Bundle\FrameworkBundle\Test\KernelTestCase not found


In KernelTestCase.php line 24:

  Class PHPUnit\Framework\TestCase not found

The error is due to the following file:

<?php
/**
 * This file is part of the RestExtraBundle package [1].
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this[1] source code.
 *
 * @license    MIT License
 * [1] http://ift.tt/2E2p6HC
 */
namespace AppBundle\Test;

use Symfony\Bundle\FrameworkBundle\Test\WebTestCase as BaseWebTestCase;

/**
 * @author William Durand <william.durand1@gmail.com>
 */
abstract class WebTestCase extends BaseWebTestCase
{
    protected function assertJsonResponse($response, $statusCode = 200)
    {
        $this->assertEquals(
            $statusCode, $response->getStatusCode(),
            $response->getContent()
        );
        $this->assertTrue(
            $response->headers->contains('Content-Type', 'application/json'),
            $response->headers
        );
    }

    protected function jsonRequest($verb, $endpoint, array $data = array())
    {
        $data = empty($data) ? null : json_encode($data);
        return $this->client->request($verb, $endpoint,
            array(),
            array(),
            array(
                'HTTP_ACCEPT'  => 'application/json',
                'CONTENT_TYPE' => 'application/json'
            ),
            $data
        );
    }
}

The file is in the following directory structure:

.
├── AppBundle.php
├── Controller
│   ├── DefaultController.php
│   └── FooController.php
└── Test
    └── WebTestCase.php

And that WebTestCase class is used in the following file:

<?php

namespace Tests\AppBundle\Controller;

use AppBundle\Test\WebTestCase;

class FooControllerTest extends WebTestCase
{
    public function testFooAction()
    {
        $client = static::createClient();

        $crawler = $client->request('GET', '/foo');

        $this->assertEquals(200, $client->getResponse()->getStatusCode());
        $this->assertJsonResponse($client->getResponse());
    }
}

Which is in the following path inside the tests directory:

.
└── AppBundle
    └── Controller
        ├── DefaultControllerTest.php
        └── FooControllerTest.php

The tests run without any kind of problem, and I actually discovered this error by chance. If I remove that file and any references to it from the tests then I can check debug:autowiring without any hassle. However I can't figure out what I am missing here. I guess it has something to do with file placement or something, but I don't really know. Can you lend me a hand please?

Also, if I didn't check that command, I wouldn't have noticed these errors. In order to avoid committing code to a repository which generates this kind of errors in the future, does Symfony log these errors somewhere? Or do I have to manually check every debug command?

Thank you in advance for your help.