PHPUnit separate connection to mysql test database Laravel 5.2 not working

I am trying to connect my Testcase integration tests to a separate database connection but its not happening. The test suite keeps connecting to the default database connection instead.

In phpunit.xml I have set this variable: <env name="DB_CONNECTION" value="mysql_testing"/>

And in my database.php I have this:

'mysql_testing' => [
            'driver' => 'mysql',
            'host' => env('DB_HOST', 'localhost'),
            'port' => env('DB_PORT', '3306'),
            'database' => env('TEST_DB', 'forge'),
            'username' => env('DB_USERNAME', 'forge'),
            'password' => env('DB_PASSWORD', ''),
            'charset' => 'utf8',
            'collation' => 'utf8_unicode_ci',
            'prefix' => '',
            'strict' => false,
            'engine' => null,
        ],

In my .env I have also set TEST_DB=flyer_test.

so why does my test suite try and connect to my default database connection? What am I doing wrong?