X Testing Software

This page provides infomation on various tools to aid the testing ( and to a degree, debugging ) of X Servers and Clients.

Please add anything I've missed that you find useful.

General Testing/Debugging Tools ( Not X specific )


GNU interactive debugger.


gcov, gprof

Code coverage and profiling. Part of the GCC compiler collection.



Valgrind is a GPL'd system for debugging and profiling x86-Linux ( and now powerpc ? ) programs. Very useful for trapping memory leaks.


X Server Testing


EricAnholt 's program for testing server render acceleration correctness. In initial development, available from fd.o git "xapps/rendercheck/"

Xtest suite

Build and usage instructions can be found here: http://wiki.x.org/wiki/XorgTesting


Tests performance of most ( non render ext ) X operations.

Available packaged in most distributions.


I did some tests measuring blit speeds with kdrive on various ARM based handhelds. The results of which are available here;


X Client Testing

Client X servers ( or X clients that are servers )

Xephyr, Xnest

Both of these provide servers that run on an existing X server. Useful for window manager development or 'emulation' of a different sized display. Both are available in git. Xnest is mature and stable but lacks support for 'modern' X extensions ( such as render and composite ), whilst Xephyr supports these extensions but is a newer and less widely distributed application.

Xnest is also available packaged in most distributions.

See also Software/Xephyr

Server side resource leaks


Provides realtime 'top' like statistics of each clients resource usage in the server. Software/xrestop

EWMH/ICCCM compliance

Window manager tools.

matchbox & metacity window manager source both contain various tools to generate 'dummy' windows with particular properties.

http://matchbox.handhelds.org ( grab matchbox-tests )



Command line tool to inspect window properties. Available packaged for most distributions.


New nice window inspection tool with GTK GUI and EWMH hint 'aware'. Software/wininfo

Protocol usage / events


xev displays the contents on events recieved by its window. Available packaged for most distributions.


xmon is an 'interactive X protocol monitor'. It acts as a proxy between a server and clients and provides configurable infomation on the traffic passing through it. Available packaged for most distributions. ( apt-get install xmon on Debian )

Also see

Automating Usage


Xnee is a suite of programs that can record and replay X events. This allows user interaction to be recorded and played back. Xnee can be used as a monitor, to 'retype' a file and to distribute events. Xnee can record all data in the X11 protocol. http://www.sandklef.com/xnee/



'matchbox nest' is a graphical wrapper around xnest. Its intended for embedded developers that want to simulate a target device ( with display, buttons ) on a desktop machine. http://matchbox.handhelds.org/sources/matchbox-nest/ -- ?MatthewAllum - 09 Jun 2004