Pay particular attention to effects such as lighting a match with a torch, vs. a torch with a match, and lighting one torch with a second. Check to confirm that a liquid can not be carried in a player's hands. As a tester, make certain that the objects' states change when one part of the puzzle is solved, to avoid nonsensical repetition. An example of this type of bug might be a vending machine that drops a bag of chips into a bin after a player inserts a coin and pushes a button. Check to make sure that, if the player pushes the button again, the text for the chips does not appear a second time.
Puzzles involving timing are the most complex to implement.
As a final note, keep your old reports and re-check all the bugs later, after the author has sent an update. Make sure the bug fixes work without causing further bugs, and that they don't disrupt the overall logic of the game in any serious way. Playtester Ethics Finding bugs is not the only concern of a beta-tester. Believe it or not, the job can also raise concerns about proper ethical behavior. Game authors put a lot of trust in their testers, and it's important that the testers not betray that trust.