Years ago, a dedicated infrastructure for facilitating language technology development was set up by the Divvun language technology development group at the University of Troms.

We present a case study of using the infrastructure while developing a morphological description for Estonian. We are interested in how the environment helps a linguist to focus on the actual linguistics, and supports reuse of code, by which we mean reuse of dedicated scripts and make-files to manipulate the language-specific source material into FST.

The paper's concern is what is the best practice to use with different FST programming language files lexc, twol and xfst – how one should write the expressions, and what conventions should be followed. In many cases there are alternative ways for describing the phenomena, and the choice will prove to be good or bad only after a considerable amount of effort has been put into following it.