Map the limits before you try to break them
List rules with a threshold. If a gate opens at three keys, check two keys, exactly three, and four keys if the player can collect extras. If a platform ends at a screen boundary, approach it slowly, quickly, and while jumping. If the timer ends a round at zero, observe the frame just before zero, the transition at zero, and an input immediately afterward. These cases expose off-by-one logic and overlapping transitions.
Probe time and repeated input
Press an action once, hold it, and tap it rapidly. These patterns can reveal whether a jump repeats, a menu advances twice, or one pickup is counted more than once. Test input just before and just after a state change, such as pressing restart as a game-over overlay appears. If the game animates with requestAnimationFrame, background tabs can affect when animation callbacks run; include a hide-and-return case for mechanics that depend on elapsed time.
Questions about testing game boundaries
What does “just below, at, and above” mean in a game test?
Choose values on both sides of a rule threshold and exactly on it. For a three-key gate, test with two keys, three keys, and any reachable count above three.
Are hidden-tab pauses always a bug?
No. Decide whether time should pause or continue while hidden, then test the chosen behavior. The important part is that timers and animation resume according to a clear rule.