Automating Internet Explorer

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Introduction

I attended an ASP.NET Users Group meeting and saw a presentation given by Demetrie Gerodimos. He is an Architect at Dell and was giving a presentation on Test Driven Development. An interesting point of his presentation for me was when he explained how they execute their tests. A discussion with him after the meeting revealed that they were automating Internet Explorer to test their ASPX pages.

After spending some time researching how easily you can automate Internet Explorer in C# (with the help of some URLs given to me by Demetrie), I began writing my own version of IEDriver. The URLs I looked at had a basic example of how to instruct IE to perform various actions. Over the course of the last year, I have enhanced my IEDriver class to handle other types of interactions with IE that I have required. While this is by no means a complete automation class, I believe it performs many of the common functions needed when writing automated tests.

Background

The basic idea here is that we will use Interop services to invoke methods on the COM interfaces built into Internet Explorer. I have written this article because the documentation available on these interfaces is scarce at best. I have spent a lot of time researching on the web and doing trial and error experimentation with these interfaces to produce much of this IEDriver class.

Using the code

The gist of it is a class called IEDriver. This class' constructor will create a new IEXPLORE.EXE process and attach to it. From then on, the methods on the IEDriver class can be used to simulate a user using his browser. While I have not implemented every type of interaction you could have with your browser, I have implemented most of the routines that I have needed to write automated tests for my product.

I have tried to hide the inner workings of the driver from the user of the class. You will notice that there are ClickXXX methods and GetXXX values that will deal with all the COM interfaces to perform the actions necessary or return the value you are interested in.

Here is an example of how easy this class is to use. This example will simply navigate to Google and search for "Automating Internet Explorer":

IEDriver driver = new IEDriver();
driver.Navigate("http://www.google.com");
driver.SetInputStringValue("q", "Internet Explorer Automation");
driver.ClickButton("btnG");

In this example, "q" is the name of the input control and "btnG" is the name of the button control on the Google page. Preferably, you will have ID attributes on your HTML elements, but if there is no ID attribute, the driver will find the element with a name attribute.

In order to use this code, you will need to do a couple of things. First of all, you will need to add a couple of references to your project. To do this, right click on References and click Add Reference:

Right click references and select Add Reference

When the Add Reference dialog comes up, first select the .NET tab. Scroll down to the Microsoft.MSHtml object, and click the Select button.

Select the Microsoft.mshtml .Net object

Next, click on the COM tab. Scroll down to the Microsoft Internet Controls object and click the Select button.

Select the Microsoft Internet Controls COM object

Now click on OK. This will add the necessary references to your project that will allow IEDriver class to make the necessary calls to automate IE.

Once you have added the appropriate references to your project, just include the IEDriver in your project. Now, all you have to do is import the IEAutomation namespace into your class and you can begin writing automated tests using IE.

Points of Interest

One thing to keep in mind. The documentation on this stuff is not very good so if you need to enhance IEDriver to support a feature that it currently doesn't, your best bet is probably to use your intellisense to invoke a method that you think might do what you want, and assign the variable to some temporary local variable. Then, fire up your debugger and use the watch window to find out all you can about the objects returned.

Tips

While writing my own automated tests, I have discovered that it is useful to extend the IEDriver class and add methods that do tasks that I might perform quite often so that I can use the intellisense and the compiler to eliminate the possibility of mistyping control names. For example:

class MyIEDriver : IEDriver {
    public void ClickSave() {
        ClickButton("SaveButton");
    }
}

This gives you compiler checking for things that may normally only be caught at runtime.

History

2-23-2005: Initial release.

License

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