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Test-Driving X11 GUIs

by George Nistorica
February 02, 2006

Driving X11 GUIs using X11::GUITest

Introduction

Interfaces to GUI applications like DCOP or D-BUS allow you to interact with GUI applications in order to get at their internal states or set some arbitrary states.

Sometimes GUIs don't allow for such interaction and you need to "click" them. If you're writing such an application, you need some sort of regression tests for it to make sure your widget/windows are as accessible as they should be. If this is the case, there is a Perl module to help you: X11::GUITest.

Be aware that X11::GUITest allows you to drive a GUI, but you can't "read" data written in a widget, such as a button or an edit box. More on this in the Limitations section below.

To install X11::GUITest, run:

$ perl -MCPAN -e 'shell'
install X11::GUITest
quit

A Simple Example

I've included two example programs. One is tested.pl and it serves as an example GUI. The other is tester.pl that starts and drives the tested program.

You need Tk installed for the tested GUI. Tk comes as a package in most GNU/Linux distributions or other *NIX OSes. Download both files in the same folder, run ./tester.pl, and watch.

What are they doing and how do they work?

Starting a GUI

First thing to do prior to driving a GUI is to start the driven program. While you can use fork and exec or any other means, X11::GUITest comes with a routine of its own.

Use StartApp( $tested_application ); to start a GUI, which results in starting the desired application in an asynchronous manner.

If you want to start an application and wait for it to finish before going on, use RunApp.

Finding a Window

After having the GUI started, you need to search for it among the other open windows on your desktop. For this, use FindWindowLike(), WaitWindowLike(), or WaitWindowViewable(), depending on what you need. Their names are pretty much self-explanatory.

Usually you need to have only one instance of the tested application started:

@windows = FindWindowLike( $tested_app_title );
print "* Number of $tested_app_title windows found: ", scalar @windows, "\n";

if ( @windows == 1 ) {
     print "* Only one instance found, going on ...\n";
} else {
    print "* The number of $tested_app_title instances is different than 1\n";
    print "exiting ...\n";
    exit;
}

FindWindowLike() returns a list of windows that match the search criteria, which is a regular expression to match against the window title. In case there is more than one window that matches the criteria, either you have the same window started multiple times, or the regular expression isn't specific enough.

Sending Keyboard Events to an Application

Having found the window, (when you know that there is only one, you can access it as the first element of @windows, namely $windows[0]), you probably want to send it some keystrokes. Use SendKeys() to do this.

If you are having a busy X server, or just want your testing to be easy for the human eye to watch, set the delay between the keystrokes (in milliseconds) with SetKeySendDelay():

SetKeySendDelay( $delay );

To send Alt+O, followed by a delay of $delay milliseconds, then e:

SendKeys( '%(o)e' );

Besides sending plain text to an application, like sending the infamous "Hello World" to an editor window, you may have noticed that the previous example sent a combination of keys. Do so by using modifiers. The modifier keys are:

• ^, Ctrl
• %, Alt
• +, Shift

The X11::GUITest documentation has a complete list of special keys and their "encodings."

You may also find it useful to use QuoteStringForSendKeys() in the case of complicated strings.

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