testInvariants(rangeSet);
    assertThat(rangeSet.asRanges()).contains(Range.closedOpen(1, 6));
    assertThat(rangeSet.complement().asRanges())
        .containsExactly(Range.lessThan(1), Range.atLeast(6))
        .inOrder();
  }

  public void testFillHoleWithOverlap() {
    TreeRangeSet<Integer> rangeSet = TreeRangeSet.create();
    rangeSet.add(Range.closedOpen(1, 3));

    rangeMap.put(Range.closedOpen(7, 10), 2);
    rangeMap.put(Range.closedOpen(12, 15), 2);
    rangeMap.put(Range.closedOpen(18, 19), 3);

    rangeMap.putCoalescing(Range.closedOpen(-5, -4), 0); // disconnected
    rangeMap.putCoalescing(Range.closedOpen(-6, -5), 0); // lower than minimum

    rangeMap.putCoalescing(Range.closedOpen(2, 4), 1); // between

    assertEquals(map, Maps.subMap(map, Range.closedOpen(0, 12)));
    assertEquals(ImmutableSortedMap.of(2, 0), Maps.subMap(map, Range.closedOpen(0, 4)));
    assertEquals(ImmutableSortedMap.of(2, 0, 4, 0), Maps.subMap(map, Range.closedOpen(2, 6)));
    assertEquals(ImmutableSortedMap.of(4, 0, 6, 0), Maps.subMap(map, Range.closedOpen(3, 7)));
    assertEquals(empty, Maps.subMap(map, Range.closedOpen(20, 30)));
  }

 * <tr><td>{@code (a..b]}  <td>{@code {x | a < x <= b}} <td>{@link Range#openClosed openClosed}
 * <tr><td>{@code [a..b)}  <td>{@code {x | a <= x < b}} <td>{@link Range#closedOpen closedOpen}
 * <tr><td>{@code (a..+∞)} <td>{@code {x | x > a}}      <td>{@link Range#greaterThan greaterThan}
 * <tr><td>{@code [a..+∞)} <td>{@code {x | x >= a}}     <td>{@link Range#atLeast atLeast}

    assertEquals(map, Maps.subMap(map, Range.closedOpen(0, 12)));
    assertEquals(ImmutableSortedMap.of(2, 0), Maps.subMap(map, Range.closedOpen(0, 4)));
    assertEquals(ImmutableSortedMap.of(2, 0, 4, 0), Maps.subMap(map, Range.closedOpen(2, 6)));
    assertEquals(ImmutableSortedMap.of(4, 0, 6, 0), Maps.subMap(map, Range.closedOpen(3, 7)));
    assertEquals(empty, Maps.subMap(map, Range.closedOpen(20, 30)));
  }

       */
      for (int i = 0; i < elements.size() - 1; i++) {
        assertEquals(elements.get(i) + 1, (int) elements.get(i + 1));
      }
      Range<Integer> range =
          elements.isEmpty() ? Range.closedOpen(0, 0) : Range.encloseAll(elements);
      return ContiguousSet.create(range, DiscreteDomain.integers());
    }
  }

  /**
   * Useless constructor for a class of static utility methods.
   *