public void testPutAll_nullValueUnsupported() {
    assertThrows(NullPointerException.class, () -> putAll(containsNullValue));
    expectUnchanged();
    expectNullValueMissingWhenNullValuesUnsupported(
        "Should not contain null value after unsupported putAll(containsNullValue)");
  }

  @MapFeature.Require(SUPPORTS_PUT)
  public void testPutAll_nullCollectionReference() {

   * that the call to {@code contains(null)} is permitted to throw a {@code NullPointerException}.
   *
   * @param message message to use upon assertion failure
   */
  protected void expectNullValueMissingWhenNullValuesUnsupported(String message) {
    try {
      assertFalse(message, getMap().containsValue(null));
    } catch (NullPointerException tolerated) {
      // Tolerated
    }
  }

  @Override