.isEqualTo("abc\uD8AB\uDCAB");
    // Differing valid surrogate pairs.
    assertThat(Strings.commonPrefix("abc\uD8AB\uDCABdef", "abc\uD8AB\uDCACxyz")).isEqualTo("abc");
    // One invalid pair.
    assertThat(Strings.commonPrefix("abc\uD8AB\uDCABdef", "abc\uD8AB\uD8ABxyz")).isEqualTo("abc");
    // Two identical invalid pairs.
    assertThat(Strings.commonPrefix("abc\uD8AB\uD8ACdef", "abc\uD8AB\uD8ACxyz"))

    extends AbstractImmutableMapMapInterfaceTest<String, Integer> {
  @Override
  protected Map<String, Integer> makePopulatedMap() {
    return ImmutableMap.of("one", 1);
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "minus one";
  }

  @Override
  protected Integer getValueNotInPopulatedMap() {
    return -1;
  }

  public void testEmptyMultisetPollLast() {
    assertNull(sortedMultiset.pollLastEntry());
  }

  @CollectionSize.Require(ONE)
  public void testSingletonMultisetFirst() {
    assertEquals(a, sortedMultiset.firstEntry());
  }

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(ONE)
  public void testSingletonMultisetPollFirst() {
    assertEquals(a, sortedMultiset.pollFirstEntry());

    SortedMap<String, Integer> sortedMap = makeEmptyMap();
    sortedMap.put("one", 1);
    sortedMap.put("two", 2);
    sortedMap.put("three", 3);
    return sortedMap;
  }

  @Override
  protected String getKeyNotInPopulatedMap() throws UnsupportedOperationException {
    return "minus one";
  }

  @Override
  protected Integer getValueNotInPopulatedMap() throws UnsupportedOperationException {

    extends AbstractImmutableMapMapInterfaceTest<String, Integer> {
  @Override
  protected Map<String, Integer> makePopulatedMap() {
    return ImmutableMap.of("one", 1);
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "minus one";
  }

  @Override
  protected Integer getValueNotInPopulatedMap() {
    return -1;
  }

    extends AbstractImmutableSortedMapMapInterfaceTest<String, Integer> {
  @Override
  protected SortedMap<String, Integer> makePopulatedMap() {
    return ImmutableSortedMap.of("one", 1);
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "minus one";
  }

  @Override
  protected Integer getValueNotInPopulatedMap() {
    return -1;
  }

    return ImmutableMap.of();
  }

  @Override
  protected Map<String, Integer> makePopulatedMap() {
    return ImmutableMap.of("one", 1, "two", 2, "three", 3);
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "minus one";
  }

  @Override
  protected Integer getValueNotInPopulatedMap() {
    return -1;
  }

    return ImmutableSortedMap.of();
  }

  @Override
  protected SortedMap<String, Integer> makePopulatedMap() {
    return ImmutableSortedMap.of("one", 1, "two", 2, "three", 3);
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "minus one";
  }

  @Override
  protected Integer getValueNotInPopulatedMap() {
    return -1;
  }

    return ImmutableMap.of();
  }

  @Override
  protected Map<String, Integer> makePopulatedMap() {
    return ImmutableMap.of("one", 1, "two", 2, "three", 3);
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "minus one";
  }

  @Override
  protected Integer getValueNotInPopulatedMap() {
    return -1;
  }

      return insertionOrder;
    }
  }

  private interface One {}

  private interface Two {}

  private interface Three {}

  private interface Four {}

  private interface Five {}

  static final class Impl implements One, Two, Three, Four, Five, Serializable {
    final int value;

    Impl(int value) {
      this.value = value;
    }