public void testAdd_supportedNullPresent() {
    E[] array = createArrayWithNullElement();
    collection = getSubjectGenerator().create(array);
    assertFalse("add(nullPresent) should return false", getSet().add(null));
    expectContents(array);
  }

  /**
   * Returns the {@link Method} instance for {@link #testAdd_supportedNullPresent()} so that tests

public class ListHashCodeTester<E> extends AbstractListTester<E> {
  public void testHashCode() {
    int expectedHashCode = 1;
    for (E element : getOrderedElements()) {
      expectedHashCode = 31 * expectedHashCode + ((element == null) ? 0 : element.hashCode());
    }
    assertEquals(
        "A List's hashCode() should be computed from those of its elements.",
        expectedHashCode,
        getList().hashCode());
  }

  /**

  @JsMethod
  static native String nullToEmpty(@Nullable String string) /*-{
    return string || "";
  }-*/;

  @JsMethod
  static native String emptyToNull(@Nullable String string) /*-{
    return string || null;
  }-*/;

  static CommonPattern compilePattern(String pattern) {
    throw new UnsupportedOperationException();
  }

  static boolean patternCompilerIsPcreLike() {
    throw new UnsupportedOperationException();

                                    "anyOf": [
                                        {"type": "array", "items": {"type": "string"}},
                                        {"type": "null"},
                                    ],
                                }
                            )
                            | IsDict(
                                # TODO: remove when deprecating Pydantic v1

    assertThat(encoding.decode(encoded)).isEqualTo(decoded);
  }

  private static void assertFailsToDecode(BaseEncoding encoding, String cannotDecode) {
    assertFailsToDecode(encoding, cannotDecode, null);
  }

  private static void assertFailsToDecode(
      BaseEncoding encoding, String cannotDecode, @Nullable String expectedMessage) {

      if (added < numElements) { // not enough elements immediately available; will have to poll
        E e = q.poll(deadline - System.nanoTime(), NANOSECONDS);
        if (e == null) {
          break; // we already waited enough, and there are no more elements in sight
        }
        buffer.add(e);
        added++;
      }
    }
    return added;
  }

  /**

   */
  static int smear(int hashCode) {
    return (int) (C2 * Integer.rotateLeft((int) (hashCode * C1), 15));
  }

  static int smearedHash(@CheckForNull Object o) {
    return smear((o == null) ? 0 : o.hashCode());
  }

  private static final int MAX_TABLE_SIZE = Ints.MAX_POWER_OF_TWO;

  static int closedTableSize(int expectedEntries, double loadFactor) {
    // Get the recommended table size.

@ElementTypesAreNonnullByDefault
abstract class AbstractRangeSet<C extends Comparable> implements RangeSet<C> {
  AbstractRangeSet() {}

  @Override
  public boolean contains(C value) {
    return rangeContaining(value) != null;
  }

  @Override
  @CheckForNull
  public abstract Range<C> rangeContaining(C value);

  @Override
  public boolean isEmpty() {
    return asRanges().isEmpty();
  }

  @Override

  }

  @Override
  public void testNulls() throws Exception {
    try {
      super.testNulls();
    } catch (AssertionError e) {
      assertWithMessage("Method did not throw null pointer OR element not in graph exception.")
          .that(e)
          .hasCauseThat()
          .hasMessageThat()
          .contains(ERROR_ELEMENT_NOT_IN_GRAPH);
    }
  }

   */
  Iterator<EndpointPair<N>> incidentEdgeIterator(N thisNode);

  /**
   * Returns the value associated with the edge connecting the origin node to {@code node}, or null
   * if there is no such edge.
   */
  @CheckForNull
  V value(N node);

  /** Remove {@code node} from the set of predecessors. */
  void removePredecessor(N node);

  /**