Where Do Unit Tests Come From_

Jing Yuan , Mike Holcombe, Marian Gheorghe

Abstract 
In Extreme programming unit testing is organized so that the unit tests 
are written before coding commences. For many programmers the selection 
of the test cases is something of an 'ad hoc' process. Where programmers 
are experienced in writing test sets it is common for them to use white 
box or structural test techniques. However, these rely on the structure 
of the code being available which is not the case with XP. This article 
describes a principled way of creating powerful, functional unit tests 
from informal descriptions of the units.