Laravel PHPUnit auto chose default connection

I'm trying to writing testing in Laravel with phpunit. However, when I run testing by php artisan test, laravel auto write and refresh on my main database. I've tried to create another database and set phpunit run with it but it doesn't work.

This is my phpunit.xml config:

    <php>
        <server name="APP_ENV" value="local"/>
        <server name="BCRYPT_ROUNDS" value="4"/>
        <server name="CACHE_DRIVER" value="array"/>
        <server name="DB_CONNECTION" value="testing"/>
        <server name="DB_DATABASE" value="main_testing"/>
        <server name="MAIL_MAILER" value="array"/>
        <server name="QUEUE_CONNECTION" value="sync"/>
        <server name="SESSION_DRIVER" value="array"/>
        <server name="TELESCOPE_ENABLED" value="false"/>
    </php>

The .env file:

DB_CONNECTION=mysql
DB_HOST=127.0.0.1
DB_PORT=3306
DB_DATABASE=main
DB_USERNAME=root
DB_PASSWORD=

DB_TEST_CONNECTION=testing
DB_TEST_HOST=127.0.0.1
DB_TEST_PORT=3306
DB_TEST_DATABASE=main_testing
DB_TEST_USERNAME=root
DB_TEST_PASSWORD=

Config connections in config/database.php:

'testing' => [
    'driver' => 'mysql',
    'url' => env('DATABASE_URL'),
    'host' => env('DB_TEST_HOST', '127.0.0.1'),
    'port' => env('DB_TEST_PORT', '3306'),
    'database' => env('DB_TEST_DATABASE', 'forge'),
    'username' => env('DB_TEST_USERNAME', 'forge'),
    'password' => env('DB_TEST_PASSWORD', ''),
    'unix_socket' => env('DB_TEST_SOCKET', ''),
    'charset' => 'utf8mb4',
    'collation' => 'utf8mb4_unicode_ci',
    'prefix' => '',
    'prefix_indexes' => true,
    'strict' => true,
    'engine' => null,
    'options' => extension_loaded('pdo_mysql') ? array_filter([
        PDO::MYSQL_ATTR_SSL_CA => env('MYSQL_ATTR_SSL_CA'),
    ]) : [],
],

I've add some code to test in Feature\ExampleTest.php:

    public function testBasicTest()
    {
        $admin = \App\Models\Admin::factory(10)->create();
        $response = $this->get('/');
        $response->assertStatus(200);
    }

When I run php artisan test, I want records created in main_testing database but it keeps creating in main database.

Anyone can help?