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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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Microtests and Unit Tests for z/OS Applictions

The idea of “unit testing” is pretty well-known in programming circles. Everyone has some concept of what it means and most software developers practice some form of unit testing.

Yet, there is disagreement about unit testing. If you’re trying to get a handle on this topic for purposes of supporting existing applications in a z/OS environment, you may find a lot of contradictory information online. Opinions are often presented as facts, and are defended strongly. I’d like to try to tease some of that apart so you can make practical sense of it.
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