EqualsTester tester = new EqualsTester();
    assertThrows(NullPointerException.class, () -> tester.addEqualityGroup((Object[]) null));
  }

  public void testNullObjectInEqualityGroup() {
    EqualsTester tester = new EqualsTester();
    NullPointerException e =
        assertThrows(NullPointerException.class, () -> tester.addEqualityGroup(1, null, 3));
    assertErrorMessage(e, "at index 1");
  }

            Exception rootCause = new NullPointerException();
            TransportException exception = new TransportException(rootCause);

            String result = exception.toString();

            assertNotNull(result);
            assertTrue(result.contains("TransportException"));
            assertTrue(result.contains("NullPointerException"));
            assertTrue(result.contains("\n"));
        }

    ImmutableMultiset.Builder<String> builder = ImmutableMultiset.builder();
    assertThrows(NullPointerException.class, () -> builder.add((String) null));
  }

  public void testBuilderAddAllHandlesNullsCorrectly() {
    {
      ImmutableMultiset.Builder<String> builder = ImmutableMultiset.builder();
      assertThrows(NullPointerException.class, () -> builder.addAll((Collection<String>) null));
    }

    {

    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_KEYS)
  public void testPutIfAbsent_nullKeyUnsupported() {
    assertThrows(NullPointerException.class, () -> getMap().putIfAbsent(null, v3()));
    expectUnchanged();
    expectNullKeyMissingWhenNullKeysUnsupported(
        "Should not contain null key after unsupported putIfAbsent(null, value)");
  }

    for (LoadingCache<Object, Object> cache : caches()) {
      assertThrows(NullPointerException.class, () -> cache.get(null));
      checkEmpty(cache);
    }
  }

  public void testGetUnchecked_null() {
    for (LoadingCache<Object, Object> cache : caches()) {
      assertThrows(NullPointerException.class, () -> cache.getUnchecked(null));
      checkEmpty(cache);
    }
  }

    for (LoadingCache<Object, Object> cache : caches()) {
      assertThrows(NullPointerException.class, () -> cache.get(null));
      checkEmpty(cache);
    }
  }

  public void testGetUnchecked_null() {
    for (LoadingCache<Object, Object> cache : caches()) {
      assertThrows(NullPointerException.class, () -> cache.getUnchecked(null));
      checkEmpty(cache);
    }
  }

    private Sources() {}

    /**
     * Creates a new source for the specified path.
     *
     * @param path the path to the file
     * @return a new Source instance
     * @throws NullPointerException if path is null
     */
    @Nonnull
    public static Source fromPath(@Nonnull Path path) {
        return new PathSource(requireNonNull(path, "path"));
    }

    /**

    }

    @Test
    @DisplayName("openConnection with null URL throws NullPointerException")
    void testOpenConnection_NullInput() {
        // Arrange
        Handler handler = newHandlerWith(mockCtx);

        // Act & Assert
        assertThrows(NullPointerException.class, () -> handler.openConnection(null), "Null URL should throw NPE");

    }

    @Test
    @DisplayName("accept: rejects null input with meaningful NullPointerException")
    void accept_rejectsNullInput() {
        // Arrange: defensive filter that validates input
        SmbFileFilter filter = f -> {
            if (f == null) {
                throw new NullPointerException("file must not be null");
            }
            return true; // not reached in this test
        };

            assertTrue(ex.getMessage().contains("Bad textual SID format"));
        }

        @Test
        @DisplayName("Textual constructor null throws NullPointerException")
        void testTextualConstructorNull() {
            assertThrows(NullPointerException.class, () -> new SID((String) null));
        }

        @Test
        @DisplayName("Binary constructor happy path and round-trip via toByteArray")