My proudest finds are ones where the scenario was thought of while doing the testing. Moreover, the scenario was not part of the original plan.
Sometimes, I write some obvious yet very loosely related stuff in my test plans which later turns out to be a bug. That makes me proud too.
I love the password bug we found with our automation when the code was still in development.
Suddenly one of our standard tests failed because a password was gone. I was sure I had set one, so I reset the database and ran the test again. Afterwards the password was gone again. Brought up the issue to the dev working on the new password encryption process. This bug never made it out of the development phase.
It really proved our automation approach to the team. With the database reset we could easily show the password disappearing. The simple automation of an βunrelatedβ component flagged a major issue early in the process.
Nice. I recently found a file save bug in an application in a similar way: the fileβs contents were deleted completely but only if Iβd chosen a certain file format for the save! Took a few tries to root-cause that one.