Laravel Secondary database connection does not work

I have one mysql database connection in config/database.php as below and it is working fine.

'mysql' => [
    'driver' => 'mysql',
    'host' => env('DB_HOST', '127.0.0.1'),
    'port' => env('DB_PORT', '3306'),
    'database' => env('DB_DATABASE', 'forge'),
    'username' => env('DB_USERNAME', 'forge'),
    'password' => env('DB_PASSWORD', ''),
    'charset' => 'utf8',
    'collation' => 'utf8_unicode_ci',
    'prefix' => '',
    'strict' => false,
    'engine' => null,
],

I am trying to define another alternate connection (for testing purposes) as below. (Same host but different database):

'mysql_testing' => [
    'driver' => 'mysql',
    'host' => env('DB_HOST', '127.0.0.1'),
    'port' => env('DB_PORT', '3306'),
    'database' => env('DB_DATABASE_TEST', 'forge'),
    'username' => env('DB_USERNAME_TEST', 'forge'),
    'password' => env('DB_PASSWORD_TEST', ''),
    'charset' => 'utf8',
    'collation' => 'utf8_unicode_ci',
    'prefix' => '',
    'strict' => false,
    'engine' => null,
],

where DB_DATABASE_TEST, DB_USERNAME_TEST and DB_PASSWORD_TEST are defined in .env as below:

DB_DATABASE_TEST=db_other
DB_USERNAME_TEST=usr_other
DB_PASSWORD_TEST=secret

However, this second connection does not work.

In tinker, if I try to use the new connection:

DB::connection('mysql_testing')->getPdo()
InvalidArgumentException with message 'Database [mysql_testing] not configured.'

And if I try to check the config values, mysql works but the new connection mysql_testing returns null:

Config::get('database.connections.mysql')
[
 "driver" => "mysql",
 "host" => "127.0.0.1",
 "port" => "3306",
 "database" => "***",
 "username" => "***",
 "password" => "***",
 "charset" => "utf8",
 "collation" => "utf8_unicode_ci",
 "prefix" => "",
 "strict" => false,
 "engine" => null,
]

Config::get('database.connections.mysql_testing')
null

Any idea how may I debug this issue?

via hashbrown