app-api/app/Models/OrderDetail.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class OrderDetail extends Model{

    protected $table='order_detail';

    public function get_good(){
        return $this->belongsTo(Goodtest::class,'goods_id','id');
    }

    public function order(){
        return $this->belongsTo(Ordertest::class,'order_id','id');
    }
}