rangeSet.add(Range.closed(3, 6));
    rangeSet.remove(Range.closed(3, 7));
    testInvariants(rangeSet);
    assertThat(rangeSet.asRanges()).isEmpty();
  }

  public void testRemoveAllExtendingBothDirections() {
    TreeRangeSet<Integer> rangeSet = TreeRangeSet.create();
    rangeSet.add(Range.closed(3, 6));
    rangeSet.remove(Range.closed(2, 7));
    testInvariants(rangeSet);