assertEquals(ImmutableMap.of("two", 2, "four", 4), filtered);

    filtered.clear();
    assertEquals(ImmutableMap.of("one", 1, "three", 3), unfiltered);
    assertTrue(filtered.isEmpty());
  }

  public void testFilteredEntriesIllegalPut() {
    Map<String, Integer> unfiltered = createUnfiltered();
    unfiltered.put("cat", 3);
    unfiltered.put("dog", 2);
    unfiltered.put("horse", 5);

    assertEquals(ImmutableMap.of("two", 2, "four", 4), filtered);

    filtered.clear();
    assertEquals(ImmutableMap.of("one", 1, "three", 3), unfiltered);
    assertTrue(filtered.isEmpty());
  }

  public void testFilteredEntriesIllegalPut() {
    Map<String, Integer> unfiltered = createUnfiltered();
    unfiltered.put("cat", 3);
    unfiltered.put("dog", 2);
    unfiltered.put("horse", 5);

        for (int i = 0; i < 10; i++) {
          assertEquals(unfiltered.lower(i), filtered.lower(i));
          assertEquals(unfiltered.floor(i), filtered.floor(i));
          assertEquals(unfiltered.ceiling(i), filtered.ceiling(i));
          assertEquals(unfiltered.higher(i), filtered.higher(i));
        }
      }
    }
  }

  private FilteredCollectionsTestUtil() {}

    final Collection<E> unfiltered;
    final Predicate<? super E> predicate;

    FilteredCollection(Collection<E> unfiltered, Predicate<? super E> predicate) {
      this.unfiltered = unfiltered;
      this.predicate = predicate;
    }

    FilteredCollection<E> createCombined(Predicate<? super E> newPredicate) {
      return new FilteredCollection<>(unfiltered, Predicates.and(predicate, newPredicate));
    }

      Multimap<K, V> unfiltered, final Predicate<? super K> keyPredicate) {
    if (unfiltered instanceof SetMultimap) {
      return filterKeys((SetMultimap<K, V>) unfiltered, keyPredicate);
    } else if (unfiltered instanceof ListMultimap) {
      return filterKeys((ListMultimap<K, V>) unfiltered, keyPredicate);
    } else if (unfiltered instanceof FilteredKeyMultimap) {

    SortedMap<String, Integer> unfiltered = createUnfiltered();
    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());
  }

                List<String> unfiltered = newArrayList();
                unfiltered.add("yyy");
                unfiltered.addAll(ImmutableList.copyOf(elements));
                unfiltered.add("zzz");
                unfiltered.add("abc");
                return Collections2.filter(Collections2.filter(unfiltered, LENGTH_1), NOT_YYY_ZZZ);
              }
            })

                List<String> unfiltered = newArrayList();
                unfiltered.add("yyy");
                unfiltered.addAll(ImmutableList.copyOf(elements));
                unfiltered.add("zzz");
                unfiltered.add("abc");
                return Collections2.filter(Collections2.filter(unfiltered, LENGTH_1), NOT_YYY_ZZZ);
              }
            })

    SortedMap<String, Integer> unfiltered = createUnfiltered();
    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());
  }

    final Collection<E> unfiltered;
    final Predicate<? super E> predicate;

    FilteredCollection(Collection<E> unfiltered, Predicate<? super E> predicate) {
      this.unfiltered = unfiltered;
      this.predicate = predicate;
    }

    FilteredCollection<E> createCombined(Predicate<? super E> newPredicate) {
      return new FilteredCollection<>(unfiltered, Predicates.and(predicate, newPredicate));
    }