As testers, one of our main jobs is to find and report issues with the software. We are paid to find bugs. If there are bugs in the software, and inevitably there are, testers need to do what they can to uncover them.
A major problem with this is that we can come across as very negative types of people, always bearing bad news. And we don’t stop there, we also raise issues with the process, documentation, people: “Why didn’t you do any unit testing?”, “That developer doesn’t know what working in a team means!”, “This feature needs to be documented!”, “You’re not supposed to make any changes to the code now!”
One way to avoid coming across so negatively is not raising as many bugs. But that approach is short-sighted! Another way, which is far better, is to bear good news as well as bad. I know I’m not the best coder, so when a Dev delivers a build for me to test, I know that they’ve done a better job than I would have done. Having this attitude tends to make it easy to give positive feedback on the software I’m testing. Also, as a tester, I try to do my best to test, to find and report bugs, but even then I make mistakes on a regular basis, I'm only human after all. But so are developers (believe it or not!), project managers and the pointy-haired boss.