Migrate for testing database

I install L 5.6 and try use mysql as testing database in config/database.php i have

        'mysql_test' => [
            'driver' => 'mysql',
            'host' => env('DB_TEST_HOST', '127.0.0.1'),
            'port' => env('DB_TEST_PORT', '3306'),
            'database' => env('DB_TEST_DATABASE', 'testing'),
            'username' => env('DB_TEST_USERNAME', 'homestead'),
            'password' => env('DB_TEST_PASSWORD', 'secret'),
            'unix_socket' => env('DB_TEST_SOCKET', ''),
            'charset' => 'utf8mb4',
            'collation' => 'utf8mb4_unicode_ci',
            'prefix' => '',
            'strict' => true,
            'engine' => null,
        ],

create env.testing

APP_NAME=Laravel
APP_ENV=testing
APP_KEY=base64:wPLFWzttKClidBk8oOv+lar7K9inLuzPXL4jp7zYesM=
APP_DEBUG=true
APP_URL=http://localhost

LOG_CHANNEL=stack

DB_CONNECTION=mysql_test
DB_TEST_HOST=127.0.0.1
DB_TEST_PORT=3306
DB_TEST_DATABASE=testing
DB_TEST_USERNAME=homestead
DB_TEST_PASSWORD=secret

BROADCAST_DRIVER=log
CACHE_DRIVER=file
SESSION_DRIVER=file
SESSION_LIFETIME=120
QUEUE_DRIVER=sync

REDIS_HOST=127.0.0.1
REDIS_PASSWORD=null
REDIS_PORT=6379

MAIL_DRIVER=smtp
MAIL_HOST=smtp.mailtrap.io
MAIL_PORT=2525
MAIL_USERNAME=null
MAIL_PASSWORD=null
MAIL_ENCRYPTION=null

PUSHER_APP_ID=
PUSHER_APP_KEY=
PUSHER_APP_SECRET=
PUSHER_APP_CLUSTER=mt1

MIX_PUSHER_APP_KEY="${PUSHER_APP_KEY}"
MIX_PUSHER_APP_CLUSTER="${PUSHER_APP_CLUSTER}"

and phpunit.xml

<?xml version="1.0" encoding="UTF-8"?>
<phpunit backupGlobals="false"
         backupStaticAttributes="false"
         bootstrap="vendor/autoload.php"
         colors="true"
         convertErrorsToExceptions="true"
         convertNoticesToExceptions="true"
         convertWarningsToExceptions="true"
         processIsolation="false"
         stopOnFailure="false">
    <testsuites>
        <testsuite name="Feature">
            <directory suffix="Test.php">./tests/Feature</directory>
        </testsuite>

        <testsuite name="Unit">
            <directory suffix="Test.php">./tests/Unit</directory>
        </testsuite>
    </testsuites>
    <filter>
        <whitelist processUncoveredFilesFromWhitelist="true">
            <directory suffix=".php">./app</directory>
        </whitelist>
    </filter>
    <php>
        <env name="APP_ENV" value="testing"/>
        <env name="CACHE_DRIVER" value="array"/>
        <env name="SESSION_DRIVER" value="array"/>
        <env name="QUEUE_DRIVER" value="sync"/>
        <env name="MAIL_DRIVER" value="array"/>
    </php>
</phpunit>

when I try php artisan migrate --env=testing I obtain Nothing to migrate

Where is problem in my setup MySQL as a testing db?