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Notation and Thought in Unit Testing

The paper “Notation as a Tool of Thought” by Kenneth E. Iverson of the IBM Thomas J. Watson Research Center was published in the Communications of the ACM, Volume 23, Number 8, 1980-08. It’s available online at Thanks to John Arundel ( who called attention to the paper in a tweet.

The paper deals with the way an appropriate notation influences people’s thinking in a given domain. Iverson was interested in the domain of mathematical computing, and he uses the APL language to illustrate his ideas. APL is an array-processing language Iverson developed in the 1960s. It has a following even today. You can read more about it on the APL Wiki at You can try it out online here:,

In this piece, I’m going to stretch the point a bit and apply some of the principles of notation Iverson presents in his article to a different domain: unit testing of application software.
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