TFUI in Tcl/Tk - Exploiting the Humble Dialog Box Neil Ostrove Test First User Interfaces (TFUI) are a hot topic of discussion with a very active Yahoo newsgroup. I recently needed to develop a database editing program in Tcl/Tk and, having just read "Test-Driven Development: A Practical Guide" by Dave Astels, decided to use the unit tests from that book (suitably modified for language and application) to drive the editor design. The result was small flexible application with an extremely clean Model/View/Controller design and a comprehensive set of unit tests. I believe Tcl/Tk and [incr Tcl/Tk] to be friendlier to the Test-Driven Development (TDD) of user interfaces than the original Java example. This paper reimplements the Movie List project from Dave Astels's book using [incr Tcl/Tk] and the tcltest framework. In the course of this I discuss the various aspects of TDD concentrating on the issues most relevant to developing user interfaces primarily through unit tests written in the test first style.