svoid stresstest_PositionalTokenIndex() {
  for n1 to 5:
    for n2 to 5:
      for n3 to 5: {
        printVars(+n1, +n2, +n3);
        int rand = 0;
        new PositionalTokenIndex idx;
        new LS l;
        for i to n1: l.add("a " + rand++);
        for i to n2: l.add("b " + rand++);
        for i to n3: l.add("c " + rand++);
        idx.addAll(map wordTok(l));
        printStruct(idx);
        LS out = map second(idx.byToken(0, "b"));
        assertEqualsVerbose(n2, l(out));
        if (n2 != 0)
          assertEquals(litciset("b"), asCISet(out));
      }
}

Began life as a copy of #1025689