BiPredicate<ImmutableTable<String, String, Integer>, ImmutableTable<String, String, Integer>>
        equivalence = pairwiseOnResultOf(ImmutableTable::cellSet);
    CollectorTester.of(collector, equivalence)
        .expectCollects(
            new ImmutableTable.Builder<String, String, Integer>()
                .put("one", "uno", 1)
                .put("two", "dos", 2)
                .put("three", "tres", 3)
                .build(),

/**
 * Tester for {@code Collector} implementations.
 *
 * <p>Example usage:
 *
 * <pre>
 * CollectorTester.of(Collectors.summingInt(Integer::parseInt))
 *     .expectCollects(3, "1", "2")
 *     .expectCollects(10, "1", "4", "3", "2")
 *     .expectCollects(5, "-3", "0", "8");
 * </pre>
 *
 * @author Louis Wasserman
 * @since 21.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class CollectorTester<

        TableCollectors.toImmutableTable(Cell::getRowKey, Cell::getColumnKey, Cell::getValue);
    CollectorTester.of(collector)
        .expectCollects(ImmutableTable.of())
        .expectCollects(ImmutableTable.of("one", "uno", 1), Tables.immutableCell("one", "uno", 1));
  }

  public void testToImmutableTableMergingSanityTest() {

        (ms1, ms2) -> ms1.equals(ms2) && ms1.entrySet().asList().equals(ms2.entrySet().asList());
    CollectorTester.of(ImmutableMultiset.<String>toImmutableMultiset(), equivalence)
        .expectCollects(ImmutableMultiset.of())
        .expectCollects(
            ImmutableMultiset.of("a", "a", "b", "c", "c", "c"), "a", "a", "b", "c", "c", "c");
  }

  public void testToImmutableMultisetCountFunction() {

    Equivalence<ImmutableMap<AnEnum, Integer>> equivalence =
        Equivalence.equals().<Entry<AnEnum, Integer>>pairwise().onResultOf(ImmutableMap::entrySet);
    CollectorTester.of(collector, equivalence)
        .expectCollects(
            ImmutableMap.of(AnEnum.A, 1, AnEnum.C, 2, AnEnum.E, 3),
            mapEntry(AnEnum.A, 1),
            mapEntry(AnEnum.C, 2),
            mapEntry(AnEnum.E, 3));
  }

            ImmutableSortedMultiset.<String>toImmutableSortedMultiset(
                String.CASE_INSENSITIVE_ORDER),
            equivalence)
        .expectCollects(ImmutableSortedMultiset.emptyMultiset(String.CASE_INSENSITIVE_ORDER))
        .expectCollects(
            ImmutableSortedMultiset.orderedBy(String.CASE_INSENSITIVE_ORDER)
                .addCopies("a", 2)
                .addCopies("b", 1)

            .onResultOf((ImmutableListMultimap<?, ?> mm) -> mm.asMap().entrySet().asList())
            .and(Equivalence.equals());
    CollectorTester.of(collector, equivalence)
        .expectCollects(ImmutableListMultimap.of())
        .expectCollects(
            ImmutableListMultimap.of("a", 1, "b", 2, "a", 3, "c", 4),
            mapEntry("a", 1),
            mapEntry("b", 2),
            mapEntry("a", 3),

                    ImmutableListMultimap.copyOf(mm).asMap().entrySet().asList())
            .and(Equivalence.equals());
    CollectorTester.of(collector, equivalence)
        .expectCollects(ImmutableSetMultimap.of())
        .expectCollects(
            ImmutableSetMultimap.of("a", 1, "b", 2, "a", 3, "c", 4),
            mapEntry("a", 1),
            mapEntry("b", 2),
            mapEntry("a", 3),

    filled.put("a", 1);
    filled.put("a", 2);
    filled.put("b", 2);
    filled.put("c", 3);
    CollectorTester.of(collector, equivalence)
        .expectCollects(empty)
        .expectCollects(
            filled, mapEntry("a", 1), mapEntry("a", 2), mapEntry("b", 2), mapEntry("c", 3));
  }

  public void testFlatteningToMultimap() {

    Equivalence<ImmutableSet<String>> equivalence =
        Equivalence.equals().onResultOf(ImmutableSet::asList);
    CollectorTester.of(collector, equivalence)
        .expectCollects(ImmutableSet.of("a", "b", "c", "d"), "a", "b", "a", "c", "b", "b", "d");
  }

  public void testToImmutableSet_duplicates() {
    class TypeWithDuplicates {
      final int a;
      final int b;