How to use MongoDB in Laravel Testing

I have laravel project, which I'm using two database: relational PostgresSQL and MongoDB.

I have to write feature tests to database but. I don't know how to create connection with mongo from laravel testing.

My phpunit.xml fragment file

<php>
        <env name="MONGO_DB_CONNECTION" value="mongodb"/>
        <env name="MONGO_DB_DSN" value="mongodb://localhost:27017"/>
        <env name="MONGO_DB_DATABASE" value="test"/>
        <env name="APP_ENV" value="testing"/>
        <env name="BCRYPT_ROUNDS" value="4"/>
        <env name="CACHE_DRIVER" value="array"/>
        <env name="DB_CONNECTION" value="sqlite"/>
        <env name="DB_DATABASE" value=":memory:"/>
        <env name="MAIL_MAILER" value="array"/>
        <env name="QUEUE_CONNECTION" value="sync"/>
        <env name="SESSION_DRIVER" value="array"/>
        <env name="TELESCOPE_ENABLED" value="false"/>
    </php>

config/database.php

'mongodb' => [
        'driver' => 'mongodb',
        'dsn' => env('MONGO_DB_DSN'),
        'database' => env('MONGO_DB_DATABASE', 'homestead'),
    ],

When I run test I got message:

MongoDB\Driver\Exception\ConnectionTimeoutException : No suitable servers found (serverSelectionTryOnce set): [connection refused calling hello on 'localhost:27017']

Can I use MongoDB on memory like env name 'DB_DATABASE' variable