}

    @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));
    }

        @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

    }

    // 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")

    }

    /**
     * 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

    }

    @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);

        // Constructor accepts null principal without throwing exception
        NtlmHttpServletRequest request = new NtlmHttpServletRequest(mockRequest, null);

        // getRemoteUser() will throw NPE when trying to call getName() on null principal
        assertThrows(NullPointerException.class, () -> request.getRemoteUser());
        assertNull(request.getUserPrincipal());
        assertEquals("NTLM", request.getAuthType());

        assertFalse(handle.isSMB2());
    }

    @Test
    @DisplayName("Null treeConnection throws NPE")
    void constructorNullTreeConnection() {
        // Null treeConnection throws NPE when acquire() is called
        assertThrows(NullPointerException.class, () -> new SmbTreeHandleImpl(resourceLoc, null));
    }

    @Test

    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));