Re: This is another success story of open source.
@bitbeisser,
Respectfully disagree here. Professional software designers do test extensively; and believe me - open or closed source the devs are pros who take pride in their work.
Bugs in the wild though will happen due to the sheer complexity of the system - for any decently complex system an full factorial experiment of all potential decision paths is infeasible for any reasonable length of time. One is literally trying to prove a negative.
Suggested link for starters: https://users.ece.cmu.edu/~koopman/des_s99/sw_testing/
What separates the men from the boys is how you handl a bug or design flaw. Ten days cycle time on a single report is v good.