exchange/database/seeds/NotificationSeeder.php

<?php

use Illuminate\Database\Seeder;
use App\User;
use Carbon\Carbon;

class NotificationSeeder extends Seeder
{
    /**
     * Run the database seeds.
     *
     * @return void
     */
    public function run()
    {
    	$user = User::where("email", "user@example.com")->first();
    	$admin = User::where("email", "admin@example.com")->first();

        DB::table('notifications')->insert([
            'detail' => 'This is an user seeder notification',
            'user_id' => $user->id,
            'link' => '/',
            'created_at' => Carbon::now()->format('Y-m-d H:i:s'),
            'updated_at' => Carbon::now()->format('Y-m-d H:i:s'),
        ]);

        DB::table('notifications')->insert([
            'detail' => 'This is an admin seeder notification',
            'user_id' => $admin->id,
            'link' => '/',
            'created_at' => Carbon::now()->format('Y-m-d H:i:s'),
            'updated_at' => Carbon::now()->format('Y-m-d H:i:s'),
        ]);
    }
}