this in Selenium’s get_eval() method

At Selenium Ruby site, there is a description for method get_eval(script), as following:

Gets the result of evaluating the specified JavaScript snippet. The snippet may have multiple lines, but only the result of the last line will be returned.

Note that, by default, the snippet will run in the context of the “selenium” object itself, so this will refer to the Selenium object. Use window to refer to the window of your application, e.g. window.document.getElementById(‘foo’) If you need to use a locator to refer to a single element in your application page, you can use this.browserbot.findElement("id=foo") where “id=foo” is your locator.

The special thing here is the this reference, means when invoking method get_eval() to run some javascript snippet, the this reference in snippet would refer to (redicted?) caller Selenium object but not the original belonging object.

This does differ from what we already know for window.eval() method, in which javascript snippt this still refer to the original belonging object, see below demo code:

var a = 0;
window.eval("this.a = 1"); // this refers to window object
alert(a); // a=1
alert(this.a == a) // true

Above code demos this is window object itself.

function A(){};
A.prototype = {
  f1: function(){
    return "f1";
  f2: function(){
var a = new A();
window.eval("a.f2()"); // equals to a.f2(), this in f2 refers to a.

Above code demos this in a.f2() method still refers to a, but not window object.

Generally, eval() is an evil thing.


Automation Training For TW QA

今天作为酱油党之一(徐X语,还有小刀和LeoShi同行)参加了徐X为TW QA开的Automation Training。


  • Ruby的包机制,应用的配置环境
  • Selenium RC的原理,包的四个变种。
  • 在07年就提到过的Page Object


  1. Effective
  2. QA manageable

最后,徐X介绍了几个月前他研究出的Data Flow大法。简言之,测试不是要去测试事情本身,而是要测试事情结果的确发生。听着象废话,但那张精美手绘图却惊艳得不行。用以作为切分并归纳测试案例的依据。很受用,争取撺掇一篇文章出来。