* opening the data stream.
   *
   * <p>The default implementation returns {@link Optional#absent}. Some sources, such as a {@code
   * CharSequence}, may return a non-absent value. Note that in such cases, it is <i>possible</i>
   * that this method will return a different number of chars than would be returned by reading all
   * of the chars.
   *

  public void testPollFirst() {
    assertEquals(a, navigableSet.pollFirst());
    assertEquals(values.subList(1, values.size()), copyToList(navigableSet));
  }

  @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
  public void testPollFirstUnsupported() {
    assertThrows(UnsupportedOperationException.class, () -> navigableSet.pollFirst());
  }

  @CollectionSize.Require(SEVERAL)

    return implied;
  }

  @Retention(RetentionPolicy.RUNTIME)
  @Inherited
  @TesterAnnotation
  public @interface Require {
    SetFeature[] value() default {};

    SetFeature[] absent() default {};
  }

    return implied;
  }

  @Retention(RetentionPolicy.RUNTIME)
  @Inherited
  @TesterAnnotation
  public @interface Require {
    MultimapFeature[] value() default {};

    MultimapFeature[] absent() default {};
  }

    return implied;
  }

  @Retention(RetentionPolicy.RUNTIME)
  @Inherited
  @TesterAnnotation
  public @interface Require {
    ListFeature[] value() default {};

    ListFeature[] absent() default {};
  }

  @CollectionSize.Require(ZERO)
  public void testIsEmpty_yes() {
    assertTrue("isEmpty() should return true", collection.isEmpty());
  }

  @CollectionSize.Require(absent = ZERO)
  public void testIsEmpty_no() {
    assertFalse("isEmpty() should return false", collection.isEmpty());
  }

  /*
   * We're not really testing the implementation of Stream, only that we're getting a Stream
   * that corresponds to the expected elements.
   */

  @CollectionFeature.Require(absent = KNOWN_ORDER)
  public void testStreamToArrayUnknownOrder() {
    Helpers.assertEqualIgnoringOrder(getSampleElements(), asList(collection.stream().toArray()));
  }

  @CollectionFeature.Require(KNOWN_ORDER)

  boolean allowsSelfLoops = false;
  ElementOrder<N> nodeOrder = ElementOrder.insertion();
  ElementOrder<N> incidentEdgeOrder = ElementOrder.unordered();

  Optional<Integer> expectedNodeCount = Optional.absent();

  /**
   * Creates a new instance with the specified edge directionality.
   *
   * @param directed if true, creates an instance for graphs whose edges are each directed; if

    @DisplayName("Unknown DOS error code yields empty Optional")
    void testUnknownCode() {
        Optional<Integer> noMatch = findNtStatus(0xdeadbeef);
        assertFalse(noMatch.isPresent(), "Mapping for unknown code should be absent");
    }

    @Test
    @DisplayName("Mocked consumer receives correct NTSTATUS value")
    void testConsumerInteraction() {
        final int dosErr = 0x00010001;
        final int expectedNt = 0xc0000002;

        assertGet(key, expectedValues);
        assertEquals(value, values.get(values.size() - 1));
      }
    }
  }

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutDuplicateValue() {
    List<Entry<K, V>> entries = copyToList(multimap().entries());

    for (Entry<K, V> entry : entries) {
      resetContainer();

      K k = entry.getKey();