Nowadays, we say “The Devil is in the detail”. In Musashi’s time, things could be a bit more drastic than that. A small clue – a bird suddenly bursting into flight, a change in the fall of shadows, a movement of a branch or someone hanging back from stepping through a certain doorway – might indicate the presence of a hidden attacker. Trifles like these could save your life; or more importantly, your lord’s.
For the most part, our testing jobs are not quite so life-and-death these days. Though I’ve worked on medical applications which were subject to very stringent regulation to safeguard patients and ensure that defects were minimised; in another job, if I’d gotten my testing wrong, there could ultimately have been a knock-on effect that would have affected utility bills paid by every household in the country. The financial sector also places a strong emphasis on accuracy because of both financial probity and the need to try to ensure legal compliance with money laundering regulations.
But for the most part, the ‘trifles’ we encounter are likely to be quite minor manifestations of error, though if these are things that occur in outputs, a minor error may be an outward sign of more serious issues in the code. And if the app handles a large volume of transactions, a rounding error four decimal places down may become subject to a multiplier effect and have a material impact on decisons taken in the real world using those numbers.
Even if you are not dealing with transactional apps or working in business areas subject to regulatory oversight, paying attention to small details is highly worthwhile. People notice small things. A small feature that gives them pleasure makes them think favourably of your app; a minor error that sticks out for one person may affect decisions taken about your app, your work or your company. If two apps are under consideration for purchase, and one has minor typographical or presentational issues in it and the other doesn’t, the final decision may hinge on those errors. As the saying goes, “you only have one chance to make a first impression”. Any compromise on presentation, spelling or grammar is going to be important to somebody – and they may be the decision-taker in your dealings with them.