Quantum Bug
quantum bug: (noun)
A bug in your code that is in a superposition of triggering and not triggering. Examining the state of said bug (via code inspection, accidental triggering, whatever) causes it to collapse into one of the two states permanently. All future tests exercising the bug will hit either pass or fail, depending on the collapsed state.
Note: It may seem that all quantum bugs collapse to triggering, since they are only noticeable if they trigger. In fact, the wave function for the code determines the probability of collapsing to triggering or not.
See also: heisenbug.
