Laravel testing - can't connect to DB on Unit test (but works perfectly in Feature test)?

I have defined database on phpunit.xml.

On my test I need to connect to database (Schema::getColumnListing('tablename');).

Everything works perfectly if test is in Feature folder, but in Unit folder exactly the same test returns this error:

  at C:\xampp\htdocs\dev\whatever\vendor\laravel\framework\src\Illuminate\Support\Facades\Schema.php:41
     37▕      * @return \Illuminate\Database\Schema\Builder
     38▕      */
     39▕     protected static function getFacadeAccessor()
     40▕     {
  ➜  41▕         return static::$app['db']->connection()->getSchemaBuilder();
     42▕     }
     43▕ }
     44▕

  1   C:\xampp\htdocs\dev\bookus\vendor\laravel\framework\src\Illuminate\Support\Facades\Facade.php:166
      Illuminate\Support\Facades\Schema::getFacadeAccessor()

  2   C:\xampp\htdocs\dev\bookus\vendor\laravel\framework\src\Illuminate\Support\Facades\Facade.php:255
      Illuminate\Support\Facades\Facade::getFacadeRoot()

Should I define database connection for Unit test separately somewhere else (where?) or is there anything else I'm missing here?

Thanks.