svoid test_MountainsAndValleys {
  new MountainsAndValleys mav;
  mav.values(litdoublearray(1, 5, 3, 4, 5, 5, 2));
  mav.run();
  assertEqualsVerbose(ll(1, 4), mav.highs().asList());
  assertEqualsVerbose(ll(0, 2, 6), mav.lows().asList());
}