svoid assertSetsEqual(S msg default "", Cl l1, Cl l2) {
  assertEquals("Set sizes", l(l1), l(l2));
  
  Set set2 = asSet(l2);
  fOr (O o : l1)
    if (!contains(set2, o))
      fail("Set 2 doesn't contain " + o);
  Set set1 = asSet(l1);
  fOr (O o : l2)
    if (!contains(set1, o))
      fail("Set 1 doesn't contain " + o);
}

Began life as a copy of #1034809