Always test your web application in the browser that your users will use.
This is particularly relevant if your users use IE, which we all know still behaves unexpectedly at times!
We spent a long time trying to replicate a bug until someone finally thought to try testing in IE, and it turned out to only occur in this browser because of some interesting GWT event binding behaviour. A lot of time was wasted.
You need to trust your data.
But it has to be trustworthy and therefore deserve this trust! So if you don’t, it is worth spending the time making it so. Following that…
Don’t assume anything.
“Assumption is the mother of all screw ups” – Wethern’s Law of Suspended Judgement
The following phrase has made the term unknown unknown famous:
“There are known knowns; there are things we know that we know. There are known unknowns; that is to say, there are things that we now know we don’t know. But there are also unknown unknowns; there are things we do not know we don’t know.”
Donald Rumsfeld, United States Defense Secretary of State, in Feb 2002. He was referring to the lack of evidence relating the Iraqi government with money being used to fund weapons of mass destruction for terrorist groups. This has since been widely requoted and is regarded as being a philosophical truth.
The unknown unknown then refers to circumstances that the subject has not even conceived. This is best viewed in contrast to the known unknown – circumstances that the subject is aware of, but does not know if they will be realised. In terms of risk, this unknown unknown is high, but something you cannot prepare for. So the best way is to eliminate all the known unknowns, so that you are only left with the unknown unknowns.
The philosopher Slavoj Žižek suggests a further category: the unknown known, that which we don’t know or intentionally refuse to acknowledge that we know. He argues that this is more dangerous still, as it refers to that which we pretend not to know about.
Finally, a bit of fun – test your assumptions by thinking about the following:
- A doctor in London had a brother in Manchester, who was a lawyer. But the lawyer in Manchester did not have a brother in London who was a doctor. Why?
- Three women each have two daughters, and they all go into a restaurant for a meal. There are only seven vacant seats in the restaurant, but each has a seat for herself. How do they manage it?