// GWT's TreeMap.entrySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testEntrySetRetainAllNullFromEmpty() {
    try {
      super.testEntrySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's TreeMap.entrySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testKeySetRemoveAllNullFromEmpty() {

      // GWT's TreeMap.entrySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testEntrySetRetainAllNullFromEmpty() {
    try {
      super.testEntrySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's TreeMap.entrySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testKeySetRemoveAllNullFromEmpty() {

      // GWT's HashMap.entrySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testEntrySetRetainAllNullFromEmpty() {
    try {
      super.testEntrySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's HashMap.entrySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testKeySetRemoveAllNullFromEmpty() {

      // GWT's HashMap.entrySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testEntrySetRetainAllNullFromEmpty() {
    try {
      super.testEntrySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's HashMap.entrySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testKeySetRemoveAllNullFromEmpty() {

      // GWT's TreeMap.entrySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testEntrySetRetainAllNullFromEmpty() {
    try {
      super.testEntrySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's TreeMap.entrySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testKeySetRemoveAllNullFromEmpty() {

    }

    @Test
    @DisplayName("encode should throw NPE on null input")
    void testEncodeNull() {
        assertThrows(NullPointerException.class, () -> Base64.encode(null));
    }

    @Test
    @DisplayName("decode should throw NPE on null input")
    void testDecodeNull() {
        assertThrows(NullPointerException.class, () -> Base64.decode(null));
    }

    public void oneArg(String s) {
      // Fail: missing NPE for s
    }
  }

  public void testFailOneArgDoesntThrowNpe() {
    shouldFail(new FailOneArgDoesntThrowNpe());
  }

  private static class FailOneArgThrowsWrongType extends PassObject {
    @Override
    public void oneArg(String s) {
      doThrow(s); // Fail: throwing non-NPE exception for null s
    }
  }

        @Test
        @DisplayName("toString with null challenge throws NPE")
        void testToStringWithNullChallengeThrowsNPE() {
            UniAddress dc = mock(UniAddress.class);
            when(dc.toString()).thenReturn("ANYSERVER");

            NtlmChallenge nc = new NtlmChallenge(null, dc);

            // Hexdump.toHexString will throw NPE when accessing challenge.length

    }

    // Invalid input: null reqPath leads to NPE from implementation
    @Test
    @DisplayName("handleDFSReferral throws NPE on null reqPath")
    void handleDfsReferralNullPathThrows() {
        when(locator.handleDFSReferral(any(), isNull())).thenThrow(new NullPointerException("reqPath"));
        NullPointerException npe = assertThrows(NullPointerException.class, () -> locator.handleDFSReferral(referral, null));

    /** Constructor for use by subclasses. */
    public StandardKeySet() {
      super(ForwardingSortedMap.this);
    }
  }

  // unsafe, but worst case is a CCE or NPE is thrown, which callers will be expecting
  @SuppressWarnings({"unchecked", "nullness"})
  static int unsafeCompare(
      @Nullable Comparator<?> comparator, @Nullable Object o1, @Nullable Object o2) {