expectAdded((E) null);
  }

  @CollectionFeature.Require(value = SUPPORTS_ADD, absent = ALLOWS_NULL_VALUES)
  public void testAdd_nullUnsupported() {
    assertThrows(NullPointerException.class, () -> collection.add(null));
    expectUnchanged();
    expectNullMissingWhenNullUnsupported("Should not contain null after unsupported add(null)");
  }

    expectAdded((E) null);
  }

  @CollectionFeature.Require(value = SUPPORTS_ADD, absent = ALLOWS_NULL_VALUES)
  public void testAdd_nullUnsupported() {
    assertThrows(NullPointerException.class, () -> collection.add(null));
    expectUnchanged();
    expectNullMissingWhenNullUnsupported("Should not contain null after unsupported add(null)");
  }

    assertThrows(IllegalArgumentException.class, () -> escapeAsString(SIMPLE_ESCAPER, test));
  }

  public void testNullInput() {
    UnicodeEscaper e = SIMPLE_ESCAPER;
    assertThrows(NullPointerException.class, () -> e.escape((String) null));
  }

  public void testBadStrings() {
    UnicodeEscaper e = SIMPLE_ESCAPER;
    String[] BAD_STRINGS = {
      String.valueOf(Character.MIN_LOW_SURROGATE),

    // URL escapers should throw null pointer exceptions for null input
    try {
      e.escape((String) null);
      fail("Escaping null string should throw exception");
    } catch (NullPointerException x) {
      // pass
    }

    // All URL escapers should leave 0-9, A-Z, a-z unescaped
    assertUnescaped(e, 'a');
    assertUnescaped(e, 'z');
    assertUnescaped(e, 'A');
    assertUnescaped(e, 'Z');

   * performance for unescaped strings (as measured by {@code CharEscapersBenchmark}).
   *
   * @param string the literal string to be escaped
   * @return the escaped form of {@code string}
   * @throws NullPointerException if {@code string} is null
   * @throws IllegalArgumentException if invalid surrogate characters are encountered
   */
  @Override
  public String escape(String string) {
    checkNotNull(string);

    FlagGuard guard = new FlagGuard(monitor2);
    assertThrows(IllegalMonitorStateException.class, () -> monitor1.hasWaiters(guard));
  }

  public void testNullMonitorInGuardConstructorThrowsNPE() {
    assertThrows(NullPointerException.class, () -> new FlagGuard(null));
  }

  public void testIsFair() {
    assertTrue(new Monitor(true).isFair());
    assertFalse(new Monitor(false).isFair());
  }

  public void testOccupiedMethods() {

    // URL escapers should throw null pointer exceptions for null input
    try {
      e.escape((String) null);
      fail("Escaping null string should throw exception");
    } catch (NullPointerException x) {
      // pass
    }

    // All URL escapers should leave 0-9, A-Z, a-z unescaped
    assertUnescaped(e, 'a');
    assertUnescaped(e, 'z');
    assertUnescaped(e, 'A');
    assertUnescaped(e, 'Z');

    FlagGuard guard = new FlagGuard(monitor2);
    assertThrows(IllegalMonitorStateException.class, () -> monitor1.hasWaiters(guard));
  }

  public void testNullMonitorInGuardConstructorThrowsNPE() {
    assertThrows(NullPointerException.class, () -> new FlagGuard(null));
  }

  public void testIsFair() {
    assertTrue(new Monitor(true).isFair());
    assertFalse(new Monitor(false).isFair());
  }

  public void testOccupiedMethods() {

    assertEquals(0, getMultiset().remove(null, 2));
  }

  @CollectionFeature.Require(value = SUPPORTS_REMOVE, absent = ALLOWS_NULL_QUERIES)
  public void testRemove_nullForbidden() {
    assertThrows(NullPointerException.class, () -> getMultiset().remove(null, 2));
  }

  @CollectionSize.Require(SEVERAL)
  @CollectionFeature.Require(SUPPORTS_REMOVE)
  public void testRemoveAllIgnoresCount() {
    initThreeCopies();

      Object ceilingKey = self.tailMap(key).firstKey();
      return unsafeCompare(comparator(), ceilingKey, key) == 0;
    } catch (ClassCastException | NoSuchElementException | NullPointerException e) {
      return false;
    }
  }

  /**
   * A sensible default implementation of {@link #subMap(Object, Object)} in terms of {@link