使用Nightwatch.js测试下载链接

1. 使用节点

   http

   模块并发出“ HEAD”请求
2. 例如：声明文件大小

test.js

var http = require("http");module.exports = {  "Is file avaliable" : function (client) {    var request = http.request({        host: "www.google.com",        port: 80,        path: "/images/srpr/logo11w.png",        method: "HEAD"    }, function (response) {      client        .assert.equal(response.headers["content-length"], 14022, 'Same file size');      client.end();    }).on("error", function (err) {      console.log(err);      client.end();    }).end();  }};