[takle]

On the subject of testing, I think it's important that people don't follow testing methodologies blindly.

In the 1960s, Djikstra said "Testing shows the presence, not the absence of bugs", which is true.

Testing is a good tool to prevent regressions. A form of testing that I find quite interesting - and wish more people would look into - is property based testing. A good example of this can be found here http://fsharpforfunandprofit.com/pbt/. Scott Wlaschin is also quite good at teaching across coding paradigms, not just functional.