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

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

/**
 * Base class for {@link RangeSet} tests.
 *
 * @author Louis Wasserman
 */
@GwtIncompatible // TreeRangeSet
public abstract class AbstractRangeSetTest extends TestCase {
  public static void testInvariants(RangeSet<?> rangeSet) {
    testInvariantsInternal(rangeSet);
    testInvariantsInternal(rangeSet.complement());
  }

  private static <C extends Comparable<?>> void testInvariantsInternal(RangeSet<C> rangeSet) {

    // Murmur3A, MurmurHash3 for x86, 32-bit (MurmurHash3_x86_32)
    // https://github.com/aappleby/smhasher/blob/master/src/main.cpp
    HashTestUtils.verifyHashFunction(hf, 32, 0xB0F57EE3);
  }

  public void testInvariants() {
    HashTestUtils.assertInvariants(murmur3_32());
  }

  @SuppressWarnings("deprecation")
  public void testInvalidUnicodeHashString() {
    String str =
        new String(