這個(gè)示例需要裝兩個(gè)包 koa2 和 supertest 下面已提供參考/包的鏈接

參考：https://www.npmjs.com/package/koa2
app.js 文件編輯如下

const koa = require('koa');
const app = new koa();
const result = new Promise(function(resolve,reject) {
    setTimeout(function(){
        resolve('Hello World');
    },1000)
});
app.use(async(ctx,next)=>{
    const start = new Date();
    ctx.body = await result;
});
app.listen(3000);
export default app;

參考：https://www.npmjs.com/package/supertest
servertest.js 文件編輯如下

var app = require('./app');
var request = require('supertest').agent(app.listen());

describe('Hello World',function(){
    it('should say "Hello World"',function(done){
        request
        .get('/')
        .expect(200)
        .expect('Hello World',done);
    });
});

可參考的實(shí)例 demo ：https://github.com/sunxiaochuan/koatest