import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;

class UrlSourceTest {

    @Test
    void testUrlSource() {
        NullPointerException e = assertThrows(
                NullPointerException.class, () -> new UrlSource(null), "Should fail, since you must specify a url");
        assertEquals("url cannot be null", e.getMessage());
    }

    Logger
      .getLogger("okhttp3")
      .addHandler(testHandler)
    Logger
      .getLogger(Http2::class.java.name)
      .addHandler(testHandler)
    Logger
      .getLogger(TaskRunner::class.java.name)
      .addHandler(testHandler)
    Logger
      .getLogger(OkHttpClient::class.java.name)
      .addHandler(testHandler)

    server.enqueue(MockResponse(body = "abc"))

    val request =

            return stringPart.toString() + digitPart.toString();
        }
    }

    /**
     * Represents a version list item. This class is used both for the global item list and for sub-lists (which start
     * with '-(number)' in the version specification).
     */
    private static class ListItem extends ArrayList<Item> implements Item {
        @Override
        public int getType() {
            return LIST_ITEM;
        }

        .isEqualTo(new byte[] {(byte) 1, (byte) 0, (byte) 0});
  }

  public void testEnsureCapacity_fail() {
    assertThrows(IllegalArgumentException.class, () -> Bytes.ensureCapacity(ARRAY1, -1, 1));
    assertThrows(IllegalArgumentException.class, () -> Bytes.ensureCapacity(ARRAY1, 1, -1));
  }

  public void testToArray() {
    // need explicit type parameter to avoid javac warning!?

}
```

## 8. Performance Metrics

### 8.1 Channel Statistics
```java
public class MultiChannelStatistics {
    private final Map<String, ChannelStatistics> channelStats;
    
    public class ChannelStatistics {
        private final AtomicLong bytesSent = new AtomicLong();
        private final AtomicLong bytesReceived = new AtomicLong();

import org.opensearch.search.aggregations.bucket.terms.TermsAggregationBuilder;

/**
 * Helper class for managing crawling information and statistics.
 * Provides functionality to track crawling sessions, manage document expiration,
 * and handle crawling information storage and retrieval.
 */
public class CrawlingInfoHelper {

    /**
     * Creates a new instance of CrawlingInfoHelper.
     */

import org.codelibs.fess.crawler.service.DataService;
import org.codelibs.fess.crawler.service.UrlQueueService;

import jakarta.annotation.Resource;

/**
 * The Crawler class is the main class for web crawling. It manages the crawling process,
 * including adding URLs to the queue, filtering URLs, managing crawler threads,
 * and handling the overall crawling lifecycle.
 *

import java.util.HashSet;
import java.util.Set;

import org.codelibs.fess.mylasta.direction.FessConfig;
import org.codelibs.fess.unit.UnitFessTestCase;
import org.codelibs.fess.util.ComponentUtil;

public class PingResponseTest extends UnitFessTestCase {

    private FessConfig originalConfig;

    @Override
    public void setUp() throws Exception {
        super.setUp();

 *
 * @author Louis Wasserman
 * @since 33.2.0 (available since 21.0 in guava-jre)
 */
@GwtCompatible
@IgnoreJRERequirement // Users will use this only if they're already using streams.
public final class MoreCollectors {

  /*
   * TODO(lowasser): figure out if we can convert this to a concurrent AtomicReference-based
   * collector without breaking j2cl?
   */

    factory.tearDown();
  }

  static ImmutableList<Method> getTestMethods(Class<?> testClass) {
    List<Method> result = new ArrayList<>();
    for (Method method : testClass.getDeclaredMethods()) {
      if (Modifier.isPublic(method.getModifiers())
          && method.getReturnType() == void.class
          && method.getParameterTypes().length == 0
          && method.getName().startsWith("test")) {