DfsReferralDataInternal result = mockReferralData.combine(null);
            assertNotNull(result);

            // Test with concrete implementation - combine with null throws NPE
            assertThrows(NullPointerException.class, () -> concreteImplementation.combine(null));
        }

        @Test
        @DisplayName("Should handle null in append")
        void testAppendWithNull() {

        sut.close();

        verify(handle, never()).close(anyLong());
    }

    // Invalid input: constructing with null handle and invoking watch() NPEs
    @Test
    @DisplayName("Null handle causes NPE on watch() (invalid input)")
    void constructor_nullHandle_watch_throwsNPE() {
        SmbWatchHandleImpl sut = new SmbWatchHandleImpl(null, 0, false);

        assertThrows(NullPointerException.class, () -> {

        void testToStringWithNullBinding() {
            // Given: Handle with null binding
            TestDcerpcHandle handleWithNullBinding = new TestDcerpcHandle(mockContext);

            // When/Then: Should throw NPE for null binding (expected behavior)
            assertThrows(NullPointerException.class, () -> handleWithNullBinding.toString());
        }

        @Test
        @DisplayName("Should handle session key retrieval")

            // The implementation doesn't check for null in constructor
            buffer = new DfsReferralRequestBuffer(path, maxReferralLevel);
            assertNotNull(buffer);

            // Will throw NPE when trying to call size() or encode()
            assertThrows(NullPointerException.class, () -> {
                buffer.size();
            });
        }

        @ParameterizedTest

    void testConstructorWithNullDelegate() {
        // When & Then
        assertDoesNotThrow(() -> {
            new DelegatingConfiguration(null);
        }, "Constructor should accept null delegate (though it would cause NPE on use)");
    }

    @Test
    @DisplayName("Constructor should store delegate reference")
    void testConstructorStoresDelegate() {
        // Given
        Configuration testDelegate = mock(Configuration.class);

            oplockLevelField.setAccessible(true);
            oplockLevelField.set(notification, (byte) 0x01);

            // The implementation calls Hexdump.toHexString which throws NPE on null
            // This test verifies the actual behavior
            assertThrows(NullPointerException.class, () -> notification.toString());
        }

        @ParameterizedTest

    void resolveSids_invalidInputs() throws Exception {
        SIDCacheImpl cache = new SIDCacheImpl(mock(CIFSContext.class));
        CIFSContext ctx = mock(CIFSContext.class);

        // Null sids array -> NPE
        assertThrows(NullPointerException.class, () -> cache.resolveSids(ctx, "server", null, 0, 1));

        // Bad offset/length leads to ArrayIndexOutOfBoundsException

        } catch (final CrawlingAccessException e) {
            // ok
        }
    }

    public void test_accessTimeout_null_safety() {
        // Test that accessTimeoutTask null check prevents NPE
        GcsClient client = new GcsClient() {
            @Override
            protected ResponseData processRequest(final String uri, final boolean includeContent) {

            if (server != null) {
                server.stop();
            }
        }
    }

    public void test_accessTimeout_null_safety() {
        // Test that accessTimeoutTask null check prevents NPE
        FtpClient client = new FtpClient() {
            @Override
            protected ResponseData getResponseData(final String uri, final boolean includeContent) {
                // Simulate quick completion before timeout

        } catch (final CrawlingAccessException e) {
            // ok
        }
    }

    public void test_accessTimeout_null_safety() {
        // Test that accessTimeoutTask null check prevents NPE
        StorageClient client = new StorageClient() {
            @Override
            protected ResponseData processRequest(final String uri, final boolean includeContent) {