assertEquals(1, filtered.size());
    assertTrue(filtered.containsEntry("foo", 1));
    assertTrue(filtered.keySet().retainAll(Arrays.asList("cat", "dog")));
    assertEquals(0, filtered.size());
  }

  // TODO(jlevy): Many more tests needed.

    assertTrue(multimap.containsKey("foo"));
    assertFalse(multimap.containsKey("cat"));
    assertTrue(multimap.containsValue(1));
    assertFalse(multimap.containsValue(5));
    assertTrue(multimap.containsEntry("foo", 1));
    assertFalse(multimap.containsEntry("cat", 1));
    assertFalse(multimap.containsEntry("foo", 5));
    assertFalse(multimap.entries().isEmpty());

          Maps.immutableEntry("bar", 1),
          Maps.immutableEntry("bar", 2),
          Maps.immutableEntry("foo", 3),
          Maps.immutableEntry("bar", 3),
          Maps.immutableEntry("cat", 2));
    }

    @Override
    public Collection<Entry<String, Integer>> create(Object... elements) {
      Multimap<String, Integer> multimap = createMultimap();
      for (Object element : elements) {

    unfiltered.put("apple", 2);
    unfiltered.put("banana", 6);
    unfiltered.put("cat", 3);
    unfiltered.put("dog", 5);

    SortedMap<String, Integer> filtered = Maps.filterEntries(unfiltered, CORRECT_LENGTH);
    assertEquals("banana", filtered.firstKey());
    assertEquals("cat", filtered.lastKey());
  }

  public void testHeadSubTailMap_FilteredMap() {

    assertThat(m.keySet()).containsExactly("boy", "girl", "cat", "dog").inOrder();
    assertThat(m)
        .isEqualTo(ImmutableMap.of("boy", "tom", "girl", "tina", "cat", "kitty", "dog", "tommy"));

    // try in a different order
    m = COMMA_SPLITTER.withKeyValueSeparator(":").split("girl:tina,boy:tom,dog:tommy,cat:kitty");

  public void testCopyOfSparse() {
    Table<Character, Integer, String> table = TreeBasedTable.create();
    table.put('x', 2, "foo");
    table.put('r', 1, "bar");
    table.put('c', 3, "baz");
    table.put('b', 7, "cat");
    table.put('e', 5, "dog");
    table.put('c', 0, "axe");
    table.put('e', 3, "tub");
    table.put('r', 4, "foo");
    table.put('x', 5, "bar");
    validateTableCopies(table);
  }

  }

  @GwtIncompatible // unreasonably slow
  public void testKeySetIteration() {
    new IteratorTester<String>(
        6,
        MODIFIABLE,
        newLinkedHashSet(asList("foo", "bar", "baz", "dog", "cat")),
        IteratorTester.KnownOrder.KNOWN_ORDER) {
      private @Nullable Multimap<String, Integer> multimap;

      @Override
      protected Iterator<String> newTargetIterator() {

  }

  @GwtIncompatible // unreasonably slow
  public void testKeySetIteration() {
    new IteratorTester<String>(
        6,
        MODIFIABLE,
        newLinkedHashSet(asList("foo", "bar", "baz", "dog", "cat")),
        IteratorTester.KnownOrder.KNOWN_ORDER) {
      private @Nullable Multimap<String, Integer> multimap;

      @Override
      protected Iterator<String> newTargetIterator() {
        multimap = create();

    table = create("foo", 1, 'a', "bar", 1, 'b', "foo", 3, 'c');
    Table<String, Integer, Character> other = HashBasedTable.create();
    other.put("foo", 1, 'd');
    other.put("bar", 2, 'e');
    other.put("cat", 2, 'f');
    try {
      table.putAll(other);
      fail("Expected UnsupportedOperationException");
    } catch (UnsupportedOperationException expected) {
    }
    assertEquals((Character) 'a', table.get("foo", 1));

    assertTrue(multimap.containsKey("foo"));
    assertFalse(multimap.containsKey("cat"));
    assertTrue(multimap.containsValue(1));
    assertFalse(multimap.containsValue(5));
    assertTrue(multimap.containsEntry("foo", 1));
    assertFalse(multimap.containsEntry("cat", 1));
    assertFalse(multimap.containsEntry("foo", 5));
    assertFalse(multimap.entries().isEmpty());