*
   * @return a value.
   * @throws UnsupportedOperationException if it's not possible to make a value that will not be
   *     found in the map.
   */
  protected abstract V getValueNotInPopulatedMap() throws UnsupportedOperationException;

  /**
   * Constructor that assigns {@code supportsIteratorRemove} the same value as {@code
   * supportsRemove}.
   */
  protected MapInterfaceTest(

   *
   * @return a value.
   * @throws UnsupportedOperationException if it's not possible to make a value that will not be
   *     found in the map.
   */
  protected abstract V getValueNotInPopulatedMap() throws UnsupportedOperationException;

  /**
   * Constructor that assigns {@code supportsIteratorRemove} the same value as {@code
   * supportsRemove}.
   */
  protected MapInterfaceTest(

          supportsIteratorRemove);
    }

    @Override
    protected String getKeyNotInPopulatedMap() {
      return "four";
    }

    @Override
    protected Integer getValueNotInPopulatedMap() {
      return 4;
    }
  }

  abstract static class RowTests extends MapTests {
    RowTests(
        boolean allowsNullValues,
        boolean supportsPut,
        boolean supportsRemove,

          supportsIteratorRemove);
    }

    @Override
    protected String getKeyNotInPopulatedMap() {
      return "four";
    }

    @Override
    protected Integer getValueNotInPopulatedMap() {
      return 4;
    }
  }

  abstract static class RowTests extends MapTests {
    RowTests(
        boolean allowsNullValues,
        boolean supportsPut,
        boolean supportsRemove,

  }

  @Override
  protected String getKeyNotInPopulatedMap() throws UnsupportedOperationException {
    return "z";
  }

  @Override
  protected String getValueNotInPopulatedMap() throws UnsupportedOperationException {
    return "26";
  }

  /** Helper assertion comparing two maps */
  private void assertMapsEqual(Map<?, ?> expected, Map<?, ?> map) {