// Arrange & Act
        SMBProtocolDowngradeException ex = new SMBProtocolDowngradeException();

        // Assert - message and cause are null
        assertNull(ex.getMessage(), "Default constructor should have null message");
        assertNull(ex.getCause(), "Default constructor should have null cause");

        // Assert - toString shows class name when message is null

            assertFalse(testBlock.isResponseAsync());
            assertNull(testBlock.getNext());
            assertFalse(testBlock.allowChain(mock(CommonServerMessageBlockRequest.class)));
            assertNull(testBlock.split());
            assertNull(testBlock.createCancel());
            assertNull(testBlock.getNextResponse());
            assertFalse(testBlock.isCancel());

        assertNotNull(result);
        assertNull(result.getId());
        assertNull(result.getSessionId());
        assertNull(result.getRuleId());
        assertNull(result.getUrl());
        assertNull(result.getParentUrl());
        assertEquals(Constants.OK_STATUS, result.getStatus());
        assertNull(result.getHttpStatusCode());
        assertNull(result.getMethod());
        assertNull(result.getMimeType());

    }

    public void test_normalize_null() {
        String enc;

        enc = null;
        assertNull(encodingHelper.normalize(enc));

        enc = "";
        assertNull(encodingHelper.normalize(enc));

        enc = " ";
        assertNull(encodingHelper.normalize(enc));
    }

    public void test_normalize_default() {
        String enc;

        assertNotNull(context);
        assertNull(context.getSessionId());
        assertEquals(0, context.getActiveThreadCount().intValue());
        assertEquals(0L, context.getAccessCount());
        assertEquals(CrawlerStatus.INITIALIZING, context.getStatus());
        assertNull(context.getUrlFilter());
        assertNull(context.getRuleManager());
        assertNull(context.getIntervalController());

        Kerb5Authenticator auth = new Kerb5Authenticator((Subject) null);

        // User accessors
        assertNull(auth.getUser());
        auth.setUser(null);
        assertNull(auth.getUser());
        auth.setUser("");
        assertEquals("", auth.getUser());

        // Realm accessors
        assertNull(auth.getRealm());
        auth.setRealm("EXAMPLE.COM");
        assertEquals("EXAMPLE.COM", auth.getRealm());

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertNull;
import static org.junit.jupiter.api.Assertions.assertTrue;
import static org.mockito.ArgumentMatchers.anyInt;
import static org.mockito.ArgumentMatchers.anyString;
import static org.mockito.Mockito.mock;

        SmbNegotiation negotiationAllNull = new SmbNegotiation(null, null, null, null);

        assertNull(negotiationAllNull.getRequest());
        assertNull(negotiationAllNull.getResponse());
        assertNull(negotiationAllNull.getRequestRaw());
        assertNull(negotiationAllNull.getResponseRaw());
    }

    @Test
    @DisplayName("getRequest should return the same request instance")

        }
        try (final ResponseData responseData = s3Client.doHead("s3://fess/")) {
            assertNull(responseData);
        }
        try (final ResponseData responseData = s3Client.doHead("s3://fess/dir1/")) {
            assertNull(responseData);
        }
        try (final ResponseData responseData = s3Client.doHead("s3://fess/dir1/dir2/")) {

        assertNull(dfsImpl.getDc(mockContext, "anydomain.com"));
    }

    @Test
    void testGetDc_ConnectionFails() throws SmbAuthException {
        // Scenario: Transport connection fails when getting DC
        when(mockCredentials.getUserDomain()).thenReturn("authdomain.com");
        // When transport fails to connect, getDc returns null
        assertNull(dfsImpl.getDc(mockContext, "anydomain.com"));