Unit Testing, Scenarios and Categories: The SCAN Method – Intro

The art of unit testing lies in choosing a set of scenarios that will produce a high degree of confidence in the functioning of the unit under test across the often very large range of possible inputs.

This article, Unit Testing, Scenarios and Categories: The SCAN Method, posted on my new GitHub blog, discusses how to do this, and proposes a method introduced in a recent GitHub project, called Scenario Category ANalysis, or SCAN for short.

It begins with a section on background that includes a link to a 2018 presentation on unit testing that introduced the concept of domain partitioning as a way of breaking infinite input spaces into a finite set of subspaces. This concept is explained here, followed by a discussion of how domain categories can form the basis for a practical approach to breaking up the input space. There is a section with examples of use of category sets to develop unit test scenarios taken from a range of my own Oracle GitHub projects.

Next, Scenario Category ANalysis (SCAN) is outlined as a systematic method for deriving unit test scenarios. We conclude with a section showing the application of the method to three examples using base code from third-party articles, taken from the GitHub project on the SCAN method.

Scanners IMDB

There is an mp4 recording briefly (2m13s) going through the sections of the blog post:

Twitter recording


The contents of the article are listed below. Click on the link above to access the article.

SQL for Recursive Generation of Item Sequences

Oracle introduced recursive subquery factoring in version 11.2 of its database software. This offered a new way to write hierarchical queries, in addition to its Connect By clause, for navigating tree structures, such as an HR employee management hierarchy. It also offered the possibility to solve a wider range of problems using its more powerful form of recursion, including combinatorial optimization problems such as bin fitting (or knapsack) problems. I used the new technique to solve a number of such problems on this blog, starting in January 2013 with A Simple SQL Solution for the Knapsack Problem (SKP-1).

In this article, I focus on how the technique may be used to generate the sequences of items that form the basis of the solutions for the larger problems. In general we assume that we have a set of n items with unique identifiers, from which we want to form sequences of r items. Here are some definitions from Wikipedia to help us classify the different types of sequence possible:

Set (mathematics)

In mathematics, a set is a well-defined collection of distinct objects, considered as an object in its own right


In mathematics, a multiset (aka bag or mset) is a modification of the concept of a set that, unlike a set, allows for multiple instances for each of its elements


In mathematics, a permutation of a set is, loosely speaking, an arrangement of its members into a sequence or linear order


In mathematics, a combination is a selection of items from a collection, such that (unlike permutations) the order of selection does not matter

We can look for all sequences of r items from n, of four different types, based on the concepts above of:

  1. Set/Permutation – items may not repeat and order matters
  2. Set/Combination – items may not repeat and order does not matter
  3. Multiset/Permutation – items may repeat and order matters
  4. Multiset/Combination – items may repeat and order does not matter

Set/Permutation – items may not repeat and order matters

Suppose we have SP(r-1), the set of all (r-1)-tuples of type Set/Permutation, we can generate SP(r) by forming a set of new r-tuples from each (r-1)-tuple t(r-1)(j):

For each item i, add i on to t(r-1)(j):

t(r)(ij) = (t(r-1)(j), i)

Set/Combination – items may not repeat and order does not matter

Multiset/Permutation – items may repeat and order matters

Multiset/Combination – items may repeat and order does not matter

First we define the different types of sequences that are possible.

Initially we want to generate a set of all sequences satisfying certain generic conditions.
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Creating Open Source Projects for Database Code – Ireland Oracle User Group Conference 2020

***UPDATE, 12/04/2020: The conference was postponed indefinitely owing to COVID-19. My presentation will come out in some form at some time. Meanwhile I’m taking the opportunity to update some of my earlier Github projects with improved structure and READMEs.***

I’m speaking on ‘Creating Open Source Projects for Database Code’ at the Oracle User Group Ireland conference 2020 at 4pm on 12 March 2020 in the Gresham hotel, Dublin.

Here’s my abstract:

and here’s the agenda.

Here is a short Twitter thread with a couple of recordings with quick tips on GitHub READMEs: GitHub README tips.

I made a Twitter thread of recordings on my presentation at the 2019 conference: Writing Clean Code in PL/SQL and SQL – Twitter Recordings

#oug_ire #OUGIreland20