Not getting a promotion or having to train someone who is getting it instead of you would not be good cause to quit, in the sense that it would not let you quit and get unemployment. (You could of course simply quit, if you like.) There is no guaranty of a promotion, and a promise of a promotion may be freely reneged upon; since this not something to which you are not entitled, not getting it is not "good cause" to quit.What you are thinking of as "good cause" is actually called "constructive termination": it is when the employer changes your current job in such a way that a reasonable person would no longer believe it is economically viable to have the job, such as cutting your hours and/or pay by 1/3 or more (approximately) or transferring you so that your commute is an hour or more longer each way than it had been, or switching a day shift worker to night shift (since that could require completely unending your life).