Symfony version(s) affected: 4.3 (at least)

Description

In the context of a functional test, if the tested page throws an exception, it is silenced by Symfony. Instead of having a failing PHPUnit test, the error page (with the ghost) is generated and no exceptions are thrown. This lead to uncaught exceptions, or cryptic errors at the following assertion.

How to reproduce

<?php

namespace App\Tests;

use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;

class ItemControllerTest extends WebTestCase
{
    public function testCreateItem(): void
    {
        $client = static::createClient();
        $client->request('GET', '/page-throwing-an-exception');
        // This test is green, but shouldn't
}

Possible Solution

Throw instead of generating the error page when in the context of a functional test.