Confusing error with EasyAdmin integration test

EasyAdminEditTest.php

class EditSchoolTest extends SchoolTestCase
{
    use ResetDatabase;

    public function testItEditsASchool(): void
    {
        $admin = $this->createAdmin();

        $school = $this->createSchool();

        $client = static::createClient();

        $client->loginUser($admin->object());

        $urlGenerator = $this->getAdminUrlGenerator();

        $url = $urlGenerator
            ->setController(SchoolCrudController::class)
            ->setAction('edit')
            ->setEntityId($school->id)
            ->generateUrl();

        $client->request('GET', $url);

        self::assertResponseIsSuccessful();

        $crawler = $client->getCrawler();

        $form = $crawler->filter('form[name="School"]')->form();

        $client->submit($form, [
            'School' => [
                'name' => 'New name',
                'website' => 'https://new-website.com',
                'region' => 'New region',
                'department' => 'New department',
                'city' => 'New city',
                'address' => 'New address',
                'isPublic' => '1',
                'foundationDate' => '2020-01-01',
                'shortDescription' => 'New short description',
                'longDescription' => 'New long description',
            ]
        ]);

        self::assertResponseRedirects();

        $client->followRedirect();

        self::assertResponseIsSuccessful();

        SchoolFactory::assert()->exists([
            'name' => 'New name',
        ]);
    }
}