}

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  public void testPutNullValue_unsupported() {
    assertThrows(NullPointerException.class, () -> multimap().put(k1(), null));

    expectUnchanged();
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_KEYS})
  public void testPutNullKey() {
    int size = getNumElements();

    multimap().put(null, v3());

    assertGet(null, v3());

  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  public void testPutNullValue_unsupported() {
    assertThrows(NullPointerException.class, () -> multimap().put(k1(), null));

    expectUnchanged();
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_KEYS})
  public void testPutNullKey() {
    int size = getNumElements();

    multimap().put(null, v3());

    assertGet(null, v3());

   * examining whether the features include KNOWN_ORDER?
   */
  protected void expectContents(Collection<E> expected) {
    assertEqualIgnoringOrder(expected, actualContents());
  }

  protected void expectUnchanged() {
    expectContents(getOrderedElements());
  }

  /**
   * Asserts that the collection under test contains exactly the elements it was initialized with