How reliable is HtmlUnitDriver?

Question

Obviously, the answer to the question depends on a number of environmental factors.

In general, I'm wondering what people's experiences are with HtmlUnitDriver as a reliable tool that can be "trusted" to navigate a website basically the same way other browsers do.

Of course, I realize "the way other browsers do" is pretty nebulous; naturally every browser will have its quirks. But I am on a project where we have hundreds of acceptance test scenarios (written in JBehave) and using FirefoxDriver and InternetExplorerDriver, running all of them takes over two hours, which is kind of rough from a continuous integration standpoint. So I'm wondering if it's at least feasible that we could switch our acceptance tests over to use HtmlUnitDriver and expect much faster times with mostly the same behavior (and perhaps we could expect a handful of tests to fail using HtmlUnitDriver and specifically run those tests with a browser-based driver).

Our UI uses GWT, which may or may not complicate things (I don't know).

Basically, in others' experience, does HtmlUnitDriver operate about as well as another browser, or is it really only appropriate for very simple HTML websites with minimal JavaScript and should not be used for an enterprise web application?

Answer 1

From my experiences with using HtmlUnitDriver I would say that if you don't use it as your baseline browser when writing your tests then converting them to use it becomes a bit of a nightmare. This is especially true when it comes to javascript heavy sites.

The main reason for this is the obvious underlying use of htmlunit which, by default, uses the Rhino javascript engine. In the past I've always had to specify that HtmlUnitDriver start htmlunit using Firefox's javascript engine. This, for the most part, solved the javascript issues I was finding while running tests using HtmlUnitDriver.

One of the biggest issues I faced when it came to using the same test code for each browser was if, on the site under test, the UI developers had assigned javascript events such as onClick() to html elements such as a <span>.

The reason for this is that if you were to use WebDriver's .click() method on a WebElement representing the <span>, then htmlunit would not do anything (it expects an onClick() to be called on elements such as an <input>). To get around this I had to manually call a click() event in javascript. You can do this either by using WebDriver's JavascriptExecutor or by using a WebDriverBackedSelenium and Selenium's .fireEvent() method.

So if your site uses such events then I'd say switching to use HtmlUnitDriver could be a big task.

Despite this, I actually use HtmlUnitDriver for all my tests. However, I went through the pains of discovering all of the above a while back, so now use HtmlUnitDriver as my baseline browser when writing tests.