didn't get the array values in this unit testing in yii2 framework

<?php
namespace tests\codeception\engine;
use engine\components\BaseException;
use engine\components\BaseService;
use engine\modules\account\models\AccUser;
use engine\modules\account\models\AccUserActivity;
use yii\db\Connection;


class AccountServiceTest extends \Codeception\TestCase\Test
{

protected $tester;

protected function _before()
{
}

protected function _after()
{
}

// tests
public function testisEmailAvailalable()
{

    $email = 'alk@gmail.com';
    $dsn = 'mysql:host=localhost;dbname=rewards';
    $username = 'root';
    $password = 'password';
    $connection = new \yii\db\Connection([
        'dsn' => $dsn,
        'username' => $username,
        'password' => $password,
    ]);
    /*$connection->open();*/

    $command = $connection->createCommand('SELECT email FROM acc_user');
    $emailIds = $command->query();
    $emailIdArray = array($emailIds);
    $this->assertContains('alk@gmail.com',$emailIdArray);
}}

while running it shows the error that There was 1 failure:

---

1) Testis email availalable (AccountServiceTest::testisEmailAvailalable)

Failed asserting that an array contains 'alk@gmail.com'.

#1 /var/www/html/rewards/shopsup-rewards-web/htdocs/tests/codeception/engine/unit/AccountServiceTest.php:44

#2 tests\codeception\engine\AccountServiceTest->testisEmailAvailalable

#3 /usr/local/bin/codecept:7

what I do is..I check the 'alk@gmail.com' is present in the email field in the acc_user table.If there is error means put the correct code