Using the Internet Explorer WebDriver Implementation from Microsoft

Microsoft recently delivered an implementation of an Internet Explorer driver. This is great news, and should be a real help to users of the Selenium project. Concurrent with that release, the IEDriverServer.exe has been updated to take advantage of this new implementation.

The integration with IEDriverServer has been implemented as a new command-line switch on IEDriverServer.exe. By launching IEDriverServer.exe using the --implementation=<value> switch, you can force the executable to use a specific driver implementation. Valid values for the switch are:

• LEGACY - Uses the existing open-source driver implementation
• VENDOR - Forces the driver to use the Microsoft implementation, regardless of whether prerequisites are met, or whether the installed version of Internet Explorer is the proper version (will throw an exception when creating a new session if the prerequisites are not installed and configured properly)
• AUTODETECT - Uses the Microsoft implementation for IE 11, if the prerequisites are installed, falling back to the open-source implementation if the components are not present (still under development in the IEDriverServer.exe code)

If no value is specified, or if the value passed in is not one of those listed above, IEDriverServer.exe will use the existing open-source implementation. This is only a temporary default; the intent is for the default to shift to be the Microsoft implementation as the specification on which it is based matures.

Prerequisites

In order to use the Microsoft implementation, you'll need a few prerequisites.

• You must have the August 2014 updates to Internet Explorer installed via Windows Update
• You need to install the IE Web Driver Tool for Internet Explorer 11
• You need version 2.43.0 or higher of the language bindings and IEDriverServer.exe

Caveats and Provisos

This integration with IEDriverServer.exe should be considered experimental at the time of this writing. First, please realize that the Microsoft implementation only supports IE11. There are no announced plans for Microsoft to support other versions of Internet Explorer with this WebDriver implementation.

Also, the Microsoft implementation strictly follows the W3C WebDriver Specification. Since the spec is currently an editors' draft, it does not completely describe the WebDriver API. In other words, there are some features that are implemented in the open-source implementation that are not documented yet in the spec, which in turn means that they are not implemented in the Microsoft implementation.

Additionally, there are some small differences in the objects sent back and forth across the JSON Wire Protocol between the spec and the open-source implementation. The implications are that there may need to be changes made to the individual language bindings to pass the proper JSON payload across to the Microsoft implementation. There is considerable pressure not to update the language bindings, since, again, the spec is currently an editors' draft, and there have been bugs filed against it to have it's protocol more closely match the existing open-source language bindings' implementations.

In the interest of allowing users to be able to experiment with the Microsoft implementation, the .NET bindings have had all of the necessary protocol changes grafted in, with explicit comments in the source code to have the changes removed when the spec is finalized and all implementations are consistent. The Java bindings have a partial implementation, and can launch IEDriverServer.exe with the proper command-line parameters to enable use of the Microsoft implementation, but the protocol changes have not yet been implemented. Unfortunately, there is no timetable for this work for other language bindings.

Example

So here's an example of what the code looks like to enable and use the Microsoft implementation of the IE driver, using C# code. It's pretty straightforward.

public static void DriveIEUsingMicrosoftImplementation()
{
    InternetExplorerDriverService service =
        InternetExplorerDriverService.CreateDefaultService();
    service.Implementation = InternetExplorerDriverEngine.Vendor;
    IWebDriver driver = new InternetExplorerDriver(service);
} 

Conversely, one could launch IEDriverServer.exe with the appropriate command-line switch and use RemoteWebDriver to talk to that running instance.