assertEquals("{}", multimap.toString());
  }

  public void testEmptyMultimapWrites() {
    Multimap<String, Integer> multimap = ImmutableListMultimap.of();
    UnmodifiableCollectionTests.assertMultimapIsUnmodifiable(multimap, "foo", 1);
  }

  private Multimap<String, Integer> createMultimap() {
    return ImmutableListMultimap.<String, Integer>builder()
        .put("foo", 1)
        .put("bar", 2)

    assertEquals("{}", multimap.toString());
  }

  public void testEmptyMultimapWrites() {
    Multimap<String, Integer> multimap = ImmutableSetMultimap.of();
    UnmodifiableCollectionTests.assertMultimapIsUnmodifiable(multimap, "foo", 1);
  }

  public void testMultimapReads() {
    Multimap<String, Integer> multimap = createMultimap();
    assertTrue(multimap.containsKey("foo"));

    assertEquals("{}", multimap.toString());
  }

  public void testEmptyMultimapWrites() {
    Multimap<String, Integer> multimap = ImmutableListMultimap.of();
    UnmodifiableCollectionTests.assertMultimapIsUnmodifiable(multimap, "foo", 1);
  }

  private Multimap<String, Integer> createMultimap() {
    return ImmutableListMultimap.<String, Integer>builder()
        .put("foo", 1)
        .put("bar", 2)

   *     multimap} may or may not have {@code sampleValue} as a key.
   */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      void assertMultimapIsUnmodifiable(Multimap<K, V> multimap, K sampleKey, V sampleValue) {
    List<Entry<K, V>> originalEntries = unmodifiableList(Lists.newArrayList(multimap.entries()));

    assertMultimapRemainsUnmodified(multimap, originalEntries);

   *     multimap} may or may not have {@code sampleValue} as a key.
   */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      void assertMultimapIsUnmodifiable(Multimap<K, V> multimap, K sampleKey, V sampleValue) {
    List<Entry<K, V>> originalEntries = unmodifiableList(Lists.newArrayList(multimap.entries()));

    assertMultimapRemainsUnmodified(multimap, originalEntries);

      @Nullable Integer nullValue) {
    Multimap<String, Integer> unmodifiable =
        prepareUnmodifiableTests(multimap, permitsDuplicates, nullKey, nullValue);

    UnmodifiableCollectionTests.assertMultimapIsUnmodifiable(unmodifiable, "test", 123);

    assertUnmodifiableIterableInTandem(unmodifiable.keys(), multimap.keys());

    assertUnmodifiableIterableInTandem(unmodifiable.keySet(), multimap.keySet());