The long way through Software Craftsmanship

Types of defects

Jun 14, 2015 - 2 minute read - Comments - ethostyposwritosthinkostypes-of-defectscategorizationslashdotquoteleprechaun

Some time ago, while researching types of defects and the cost of fixing them1, I stumbled upon this:

Years ago I worked with a bunch of economists in the US Federal Government - they categorized ‘bugs’ in their memos into three types:

  • Typos: Simple misspellings of words. Infrequent, easy to detect, easy to fix.

  • Writos: Incoherent sentences. More frequent, hard to detect, harder to fix.

  • Thinkos: Conceptually bonkers. Very frequent, subtle and hard to detect; almost impossible to fix.

Most ‘late’ bugs that I’ve seen in software projects belong in the last category - a lack of design or the failure to make a working mock-up leads to ‘thinkos’ which are only obvious when the application is nearly completed. These are expensive to fix.


I would also add a new category to this:

  • Ethos: Morally wrong, although possibly legal. These may take different forms: vary from a company to the next one, from society to society, etc. Even harder to fix than ‘thinkos’, as there is a reason (mainly economic) to keep them in place.

On a technical note, these are not usually well-known artifacts in the company, therefore not everyone should know about them. Only a few developers know the correct reasons behind them and the rest might be sold a fake reason, so the latter cannot fix these ‘ethos’, as they assume they are present for a good reason

  1. This is also a chapter in the book The Leprechauns of Software Engineering by Laurent Bossavit: ‘Chapter 10: The cost of defects: an illustrated history’ [return]

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