Testing does not prevent defects

There seems to be a bunch of discussion regarding whether testers prevent defects or not.

The main source of confusion that I see is confusing ‘testers’ with ‘testing’. Clearing this up seems pretty simple.

Testing does not prevent defects. Testers may. I do. But I don’t call that part of my work ‘testing’, even if testing and experiment design is a part of that work. Clarifying which aspects of my work are ‘testing’ and which are not is important for at least two reasons.

The first, is that I can discuss those skills clearly and keep that knowledge in one place. This allows me to make shortcut reference to those skills when I apply them in other roles I may be playing.

Secondly, time I spend playing some other role that may be about defect prevention (or team/product alignment, shared focus, or anything else) usually involves (sometimes irreconcilable) tradeoffs in the quality of my testing work or less available time for test effort. If I’m not making this clear to stakeholders who matter, or if I am unaware of the potential for conflict, I expose myself to a number of potential problems.