You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: client_test.go
    path of file: ./repos/gopay/wechat
    
    the code of the file until where you have to start completion: package wechat

import (
	"context"
	"os"
	"testing"

	"github.com/go-pay/gopay"
	"github.com/go-pay/util"
	"github.com/go-pay/xlog"
)

var (
	client *Client
	appId  = "wxdaa2ab9ef87b5497"
	mchId  = "1368139502"
	apiKey = "GFDS8
    
func TestMain(m *testing.M) {

	// 初始化微信客户端
	//    appId：应用ID
	//    mchId：商户ID
	//    apiKey：API秘钥值
	//    isProd：是否是正式环境
	client = NewClient(appId, mchId, apiKey, false)

	// 打开Debug开关，输出日志
	client.DebugSwitch = gopay.DebugOn

	// 设置国家，不设置默认就是 China
	client.SetCountry(China)

	// 不使用证书接口，可以不添加证书
	// 添加pkcs12内容
	//err = client.AddCertPkcs12FilePath("apiclient_cert.p12")
	//if err != nil {
	//	panic(err)
	//}

	// 或

	// 添加pem证书路径
	//err := client.AddCertPemFilePath("apiclient_cert.pem", "apiclient_key.pem")
	//if err != nil {
	//	panic(err)
	//}

	os.Exit(m.Run())
}