@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

        TestCredentials creds = new TestCredentials("DOM", false, false, new Subject(), false);
        // Act & Assert
        NullPointerException npe = assertThrows(NullPointerException.class, () -> creds.unwrap(null));
        assertEquals("type", npe.getMessage());
    }

    @Test
    @DisplayName("clone returns a distinct copy with same properties")
    void clone_returns_copy() {
        // Arrange

    }

    /**
     * Ensure encode throws NPE when passed a null buffer.
     */
    @Test
    @DisplayName("Encode with null buffer throws NullPointerException")
    public void testEncodeNullBuffer() throws NdrException {
        NdrHyper hyper = new NdrHyper(5L);
        assertThrows(NullPointerException.class, () -> hyper.encode(null));
    }

    /**
     * Ensure decode throws NPE when passed a null buffer.
     */
    @Test

        verify(mockDir, times(3)).getPath();
        verifyNoMoreInteractions(mockDir);
    }

    /**
     * Defensive behavior: implementation throws NPE on null inputs by design.
     */
    @Test
    @DisplayName("implementation explicitly rejects nulls with NPE")
    void implementationRejectsNulls() {
        SmbFilenameFilter filter = (dir, name) -> {
            if (dir == null || name == null) {

    }

    // 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));

        assertTrue(ex.getMessage().contains("Failed to calculate MIC"));
    }

    @Test
    @DisplayName("calculateMIC with null data throws NPE")
    void calculateMIC_nullData() {
        assertThrows(NullPointerException.class, () -> ctx.calculateMIC(null));
    }

    @Test
    @DisplayName("verifyMIC delegates to GSS and succeeds")

    }

    @Test
    @DisplayName("Test write operations")
    void testWriteOperations() {
        byte[] dst = new byte[1024];

        // Initialize transaction buffer to avoid NPE
        transaction.setBuffer(new byte[SmbComTransaction.TRANSACTION_BUF_SIZE]);

        // Test parameter words wire format
        int paramWords = transaction.writeParameterWordsWireFormat(dst, 0);

        shareInfo1.netname = "TestShare";
        shareInfo1.type = 1;
        shareInfo1.remark = "Test Remark";

        // Set up deferred buffer chain to avoid NPE
        mockDeferredBuffer.deferred = mockDeferredBuffer;

        shareInfo1.encode(mockNdrBuffer);

        // Verify the encode operations
        verify(mockNdrBuffer).align(4);

    class CtorValidation {
        @Test
        @DisplayName("null handle throws NPE")
        void nullHandle() {
            assertThrows(NullPointerException.class, () -> new SmbPipeInputStream(null, tree));
        }

        @Test
        @DisplayName("null tree throws NPE")
        void nullTree() {
            assertThrows(NullPointerException.class, () -> new SmbPipeInputStream(handle, null));

            }
        }
        assertThrows(ClassCastException.class, () -> {
            OtherPipeHandle result = target.unwrap(OtherPipeHandle.class);
        });

        // Null input: document current behavior (NPE from isAssignableFrom)
        assertThrows(NullPointerException.class, () -> target.unwrap(null));
    }

    @Test
    @DisplayName("getPipe, getPipeType, getUncPath delegate to underlying pipe")