If you see code like this, you know something's quite wrong

If you see code like this, you know something's quite wrong
(present in some form since r1.1, still present in r1.31):

229                 case 013:
230                         if (randomize)
231                                 begin = BEGIN_DEF;
232                         else if (reps == 0)
233                                 errx(1, "Must specify begin if reps == 0");
234                         begin = ender - reps * s + s;

Add two tests that check for the intended behavior.