assertEquals(Range.open(2, 4), closedRange.gap(Range.atMost(2)));
  }

  // TODO(cpovirk): More extensive testing of gap().

  public void testSpan_general() {
    Range<Integer> range = Range.closed(4, 8);

    // separate below
    assertEquals(Range.closed(0, 8), range.span(Range.closed(0, 2)));
    assertEquals(Range.atMost(8), range.span(Range.atMost(2)));