*     class under test.
   */
  protected abstract Map<K, V> makePopulatedMap() throws UnsupportedOperationException;

  /**
   * Creates a new key that is not expected to be found in {@link #makePopulatedMap()}.
   *
   * @return a key.
   * @throws UnsupportedOperationException if it's not possible to make a key that will not be found
   *     in the map.

    @Override
    protected Map<String, Integer> makeEmptyMap() {
      return makeTable().row('a');
    }

    @Override
    protected Map<String, Integer> makePopulatedMap() {
      Table<Character, String, Integer> table = makeTable();
      table.put('a', "one", 1);
      table.put('a', "two", 2);
      table.put('a', "three", 3);
      table.put('b', "four", 4);

  @Override
  protected Map<String, String> makeEmptyMap() {
    return transformValues(new HashMap<String, String>(), Functions.<String>identity());
  }

  @Override
  protected Map<String, String> makePopulatedMap() {
    Map<String, Integer> underlying = new HashMap<>();
    underlying.put("a", 1);
    underlying.put("b", 2);
    underlying.put("c", 3);
    return transformValues(underlying, Functions.toStringFunction());
  }

  protected Map<String, Collection<Integer>> makeEmptyMap() {
    Map<String, Integer> map = new HashMap<>();
    return Multimaps.forMap(map).asMap();
  }

  @Override
  protected Map<String, Collection<Integer>> makePopulatedMap() {
    Map<String, Integer> map = new HashMap<>();
    map.put("foo", 1);
    map.put("bar", 2);
    map.put("cow", 3);
    return Multimaps.forMap(map).asMap();
  }

  @Override

  @Override
  protected Map<String, String> makeEmptyMap() {
    return transformValues(new HashMap<String, String>(), Functions.<String>identity());
  }

  @Override
  protected Map<String, String> makePopulatedMap() {
    Map<String, Integer> underlying = new HashMap<>();
    underlying.put("a", 1);
    underlying.put("b", 2);
    underlying.put("c", 3);
    return transformValues(underlying, Functions.toStringFunction());
  }

   * returns the same value which {@code map.get(x)} did immediately beforehand.
   */
  @Override
  public void testRemove() {
    Map<String, Collection<Integer>> map;
    try {
      map = makePopulatedMap();
    } catch (UnsupportedOperationException e) {
      return;
    }
    String keyToRemove = map.keySet().iterator().next();
    if (supportsRemove) {
      int initialSize = map.size();

    return transformValues(
        new UnmodifiableIteratorMap<String, Integer>(underlying), Functions.toStringFunction());
  }

  @Override
  protected Map<String, String> makePopulatedMap() {
    Map<String, Integer> underlying = new HashMap<>();
    underlying.put("a", 1);
    underlying.put("b", 2);
    underlying.put("c", 3);
    return transformValues(