*
 * <p>Null keys and values are permitted (provided, of course, that the respective comparators
 * support them). All optional multimap methods are supported, and all returned views are
 * modifiable.
 *
 * <p>This class is not threadsafe when any concurrent operations update the multimap. Concurrent
 * read operations will work correctly. To allow concurrent update operations, wrap your multimap

        assertEquals(123, metaDataMap.get("key2"));
        assertEquals(true, metaDataMap.get("key3"));
    }

    public void test_metaDataMapModifiable() {
        // Test that metadata map is modifiable
        ResponseData data = new ResponseData();

        data.addMetaData("key1", "value1");

        Map<String, Object> metaDataMap = data.getMetaDataMap();
        metaDataMap.put("key2", "value2");

    CacheBuilder<Object, Object> builder = createCacheBuilder().concurrencyLevel(1);
    LocalLoadingCache<Object, Object> cache = makeCache(builder, identityLoader());
    ConcurrentMap<Object, Object> map = cache.localCache; // modifiable map view
    assertThat(cache.stats()).isEqualTo(EMPTY_STATS);

    Object one = new Object();
    assertThat(map.put(one, one)).isNull();
    assertThat(map.get(one)).isSameInstanceAs(one);

  // here to provide error messages.
  // TODO(user): Some Strings used in the subclasses can be added as static Strings
  // here too.
  static final String ERROR_MODIFIABLE_SET = "Set returned is unexpectedly modifiable";
  static final String ERROR_SELF_LOOP = "self-loops are not allowed";
  static final String ERROR_ADDED_SELF_LOOP = "Should not be allowed to add a self-loop edge.";

 * will change the table.
 *
 * <p>All methods that modify the table are optional, and the views returned by the table may or may
 * not be modifiable. When modification isn't supported, those methods will throw an {@link
 * UnsupportedOperationException}.
 *
 * <h3>Implementations</h3>
 *
 * <ul>
 *   <li>{@link ImmutableTable}
 *   <li>{@link HashBasedTable}

  }

  public void testSkip_iterator() throws Exception {
    new IteratorTester<Integer>(
        5,
        IteratorFeature.MODIFIABLE,
        Lists.newArrayList(2, 3),
        IteratorTester.KnownOrder.KNOWN_ORDER) {
      @Override
      protected Iterator<Integer> newTargetIterator() {

   * suitable for testing that map entries cannot be modified via a nefarious implementation of
   * equals. This is used for testing unmodifiable collections of map entries; for example, it
   * should not be possible to access the raw (modifiable) map entry via a nefarious equals method.
   */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      Entry<K, V> nefariousMapEntry(K key, V value) {

 * will change the table.
 *
 * <p>All methods that modify the table are optional, and the views returned by the table may or may
 * not be modifiable. When modification isn't supported, those methods will throw an {@link
 * UnsupportedOperationException}.
 *
 * <h3>Implementations</h3>
 *
 * <ul>
 *   <li>{@link ImmutableTable}
 *   <li>{@link HashBasedTable}

  // here to provide error messages.
  // TODO(user): Some Strings used in the subclasses can be added as static Strings
  // here too.
  static final String ERROR_MODIFIABLE_SET = "Set returned is unexpectedly modifiable";
  static final String ERROR_SELF_LOOP = "self-loops are not allowed";
  static final String ERROR_ADDED_SELF_LOOP = "Should not be allowed to add a self-loop edge.";

   * suitable for testing that map entries cannot be modified via a nefarious implementation of
   * equals. This is used for testing unmodifiable collections of map entries; for example, it
   * should not be possible to access the raw (modifiable) map entry via a nefarious equals method.
   */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      Entry<K, V> nefariousMapEntry(K key, V value) {