import org.dbflute.utflute.core.PlainTestCase;

/**
 * Test class for AbstractRule.
 * Tests the abstract rule implementation and its common functionality.
 */
public class AbstractRuleTest extends PlainTestCase {

    /**
     * Concrete implementation of AbstractRule for testing
     */
    public static class TestAbstractRule extends AbstractRule {

import org.dbflute.utflute.core.PlainTestCase;

/**
 * Test class for Transformer interface.
 * Tests the contract and behavior of Transformer implementations.
 */
public class TransformerTest extends PlainTestCase {

    /**
     * Basic test implementation of Transformer
     */
    public static class TestTransformer implements Transformer {
        private String name;

import org.dbflute.utflute.core.PlainTestCase;

/**
 * Test class for AbstractTransformer.
 * Tests the abstract transformer implementation and its name management functionality.
 */
public class AbstractTransformerTest extends PlainTestCase {

    /**
     * Concrete implementation of AbstractTransformer for testing
     */
    public static class TestTransformer extends AbstractTransformer {

        assertNotNull(readings);
        assertEquals(1, readings.size());
        assertEquals("TEST", readings.get(0));
    }

    /**
     * Test implementation of ReadingConverter for testing purposes
     */
    private static class TestReadingConverter implements ReadingConverter {

        private boolean initialized = false;
        private int initCount = 0;

import org.dbflute.utflute.core.PlainTestCase;

/**
 * Test class for Rule interface.
 * Tests the contract and behavior of Rule implementations.
 */
public class RuleTest extends PlainTestCase {

    /**
     * Test implementation of Rule interface for testing purposes
     */
    public static class TestRule implements Rule {
        private static final long serialVersionUID = 1L;

```

### Key Components

#### Core Engine
- **Crawler**: Main orchestrator managing crawl execution
- **CrawlerContext**: Execution context and configuration
- **CrawlerThread**: Individual crawler thread implementation

#### Client Architecture
- **HcHttpClient**: HTTP/HTTPS client using Apache HttpComponents
- **FileSystemClient**: File system access
- **FtpClient**: FTP protocol support

import org.opensearch.index.query.QueryBuilders;
import org.opensearch.search.SearchHit;
import org.opensearch.search.SearchHits;

import jakarta.annotation.PostConstruct;

/**
 * OpenSearchDataService is an implementation of {@link DataService} for OpenSearch.
 */
public class OpenSearchDataService extends AbstractCrawlerService implements DataService<OpenSearchAccessResult> {

    /**

    private CrawlerContext crawlerContext;

    @Override
    protected void setUp() throws Exception {
        super.setUp();
        crawlerContext = new CrawlerContext();
    }

    /**
     * Test implementation of UrlFilter for testing
     */
    private static class TestUrlFilter implements UrlFilter {
        @Override
        public void init(String sessionId) {
        }

        @Override

import org.dbflute.utflute.core.PlainTestCase;

/**
 * Test class for RuleManager interface.
 * Tests the contract and behavior of RuleManager implementations.
 */
public class RuleManagerTest extends PlainTestCase {

    /**
     * Test implementation of RuleManager for testing purposes
     */
    public static class TestRuleManager implements RuleManager {
        private final List<Rule> rules = new ArrayList<>();

import org.codelibs.fess.crawler.entity.UrlQueue;
import org.codelibs.fess.crawler.exception.CrawlingAccessException;
import org.codelibs.fess.crawler.helper.LogHelper;
import org.codelibs.fess.crawler.log.LogType;

/**
 * Implementation of the {@link LogHelper} interface.
 * This class provides methods for logging various events during the crawling process.
 * It uses Log4j2 for logging.
 *
 * <p>