Composer dumpautoload 成功之后还是不能加载 test_helper ()?

vagrant@homestead:~/code/laravel-shop$ composer dumpautoload
Generating optimized autoload files

Illuminate\Foundation\ComposerScripts::postAutoloadDump
@php artisan package:discover
Discovered Package: fideloper/proxy
Discovered Package: laravel/tinker
Discovered Package: nesbot/carbon
Package manifest generated successfully.

vagrant@homestead:~/code/laravel-shop$ php artisan tinker
Psy Shell v0.9.6 (PHP 7.2.5-1+ubuntu18.04.1+deb.sury.org+1 — cli) by Justin Hileman

test_helper()
PHP Fatal error: Call to undefined function test_helper() in psy shell code on line 1