Today is the test day for one of our games. Luckily it's not my game being tested as it always provides some stress. As a tester you have to try to find bugs by trying many actions. If at a certain point you encounter a bug you have to remember what actions you did that led you to the bug. Then you try to reproduce the bug. If you can't reproduce it then you either forgot to do an action or the bug is very subtile or time-related. We also tag our bugs with priority. Naturally a bug that prevents game progress is a bug of high priority. Bugs like "this button has the wrong text" should be fixed but are of lower priority. Other bugs like the one shown in the screenshot below (where an explosion decal is partly in air) are not very useful to commit as they won't be fixed due to it being too hard to fix. Removing it all together however would cause lack of detail (you'd miss it).
An explosion decal is partly in air.
Luckily I didn't find many bugs in the part I was testing or perhaps I didn't test well enough (there are endless combinations) :P