PHP 7.2.3-1+ubuntu16.04.1+deb.sury.org+1 (cli)
mysql  Ver 14.14 Distrib 5.7.21, for Linux (x86_64) using  EditLine wrapper
Psy Shell v0.8.18 (PHP 7.2.3-1+ubuntu16.04.1+deb.sury.org+1 — cli)

php artisan migrate

In Connection.php line 664:

  SQLSTATE[HY000] [1045] Access denied for user 'root'@'localhost' (using pas
  sword: YES) (SQL: select * from information_schema.tables where table_schem
  a = mytestproject and table_name = migrations)

In PDOConnection.php line 50:

  SQLSTATE[HY000] [1045] Access denied for user 'root'@'localhost' (using pas
  sword: YES)

In PDOConnection.php line 46:

  SQLSTATE[HY000] [1045] Access denied for user 'root'@'localhost' (using pas
  sword: YES)

APP_ENV=local
APP_DEBUG=true
APP_KEY=
APP_TIMEZONE=UTC

DB_CONNECTION=mysql
DB_HOST=localhost
DB_PORT=3306
DB_DATABASE=mytestproject
DB_USERNAME=root
DB_PASSWORD=password

REDIS_HOST=127.0.0.1
REDIS_PORT=6379

CACHE_DRIVER=redis
QUEUE_DRIVER=redis

'mysql' => [
    'driver' => 'mysql',
    'host' => env('DB_HOST', 'localhost'),
    'port' => env('DB_PORT', '3306'),
    'database' => env('DB_DATABASE', 'mytestproject'),
    'username' => env('DB_USERNAME', 'root'),
    'password' => env('DB_PASSWORD', 'mypassword'),
    'unix_socket' => env('DB_SOCKET', ' '),
    'charset' => 'utf8mb4',
    'collation' => 'utf8mb4_unicode_ci',
    'prefix' => '',
    'strict' => true,
    'engine' => null,
],

mysql> SELECT user, host FROM mysql.user;
+------------------+-----------+
| user             | host      |
+------------------+-----------+
| debian-sys-maint | localhost |
| mysql.session    | localhost |
| mysql.sys        | localhost |
| root             | localhost |
+------------------+-----------+
4 rows in set (0.06 sec)