PHPUnit LogicException: The request was not redirected. Symfony

I am trying to test a simple registration with phpunit with a redirect, I have all the time this error:

Test class:

<?php

namespace Tests\AppBundle\Services;

use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;

class SecuriteTest extends WebTestCase
{

    private $user;

    public function __construct() {
        $this->user = static::createClient();
    }

    public function testsendCreateAccountMail(){

        $crawler = $this->user->request('GET', '/inscription');

        $this->assertEquals(1, $crawler->filter('h1:contains("Informations personnelles")')->count());

        $form = $crawler->selectButton('submitInscription')->form();

        $form['inscription[gender]']     = 'Masculin';
        $form['inscription[name]']       = 'Test';
        $form['inscription[firstName]']      = 'Test';
        $form['inscription[username]']    = 'Test-25@gmail.com';
        $form['inscription[birthDate]']    =  '05/10/1992';
        $form['inscription[pseudo]']    = 'Test';
        $form['inscription[password][first]']    = 'blablabla';
        $form['inscription[password][second]']    = 'blablabla';
        $form['inscription[account]']    = 'Particulier';
        $form['inscription[mentionsLegales]']    = '1';

        $this->user->submit($form);

        $crawler = $this->user->followRedirect();

        $this->assertEquals(1, $crawler->filter('.testFlash:contains("Vous allez recevoir une demande de confirmation sur votre adresse email")')->count());

    }
}

I also try to test with a contact form with only 3 inputs, I still have the same error.

Thank you