Phpunit symfony 4表单单元测试不工作

嗨，我想在symfony 4中测试表单。这是ismy代码

$crawler = $this->client->request('GET', '/admin/user/new');

        $form = $crawler->selectButton('Save')->form(array(
            'user[displayName]' => 'user',
            'user[username]' => 'user@yahoo.com',
            'user[password]' => 'user123',
            'user[phoneNumber]' => '1234789',
            'user[roles]' => 'ROLE_USER',
        ));
        $crawler = $this->client->submit($form);
        $this->assertGreaterThan(
                0, $crawler->filter('html:contains("Your changes were saved!")')->count()
        );

形式是有价值的但我得到的只是

断言0大于0失败

实际提交时，我收到此警报

<div class="alert alert-success alert-dismissible">
    Your changes were saved!
</div>

您的更改已保存！

---

如果有人能提供帮助，就需要遵循重定向，因为表单提交总是重定向的

$crawler = $this->client->request('GET', '/admin/user/new');

        $form = $crawler->selectButton('Save')->form(array(
            'user[displayName]' => 'user',
            'user[username]' => 'user@yahoo.com',
            'user[password]' => 'user123',
            'user[phoneNumber]' => '1234789',
            'user[roles]' => 'ROLE_USER',
        ));
        $crawler = $this->client->submit($form);

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

        $this->assertGreaterThan(
                0, $crawler->filter('html:contains("Your changes were saved!")')->count()
        );