No need to understand how it works

A decade ago, a manager once asked me why I had questions about the software-under-test and how it was supposed to work. He added: "You don't need to know all that stuff, all you need to do is test".

The exact wording of the German speaking manager was: "Wozu must du wissen, wie das funktioniert? Du sollst es nur testen".

This happened so many years back, I can't even remember whether he really meant it seriously or whether he was just teasing me. 

Anyhow, I put it here, because the more you know how a piece of software really works, the more target-oriented and effective your tests evolve. With "effective" I mean tests, that find ugly bugs.

(Source: Simply the Test)