* @param extractor the extractor to add
     * @throws CrawlerSystemException if the key list is null or empty, or if the extractor is null
     */
    public void addExtractor(final List<String> keyList, final Extractor extractor) {
        if (keyList == null || keyList.isEmpty()) {
            throw new CrawlerSystemException("The key list is empty.");
        }
        keyList.stream().distinct().forEach(key -> addExtractor(key, extractor));

        queryContext = new QueryContext(null, false);
        assertEquals("*", queryContext.getQueryString());
        assertNull(queryContext.getDefaultField());
    }

    // Test constructor with empty query string
    public void test_constructor_emptyQueryString() {
        queryContext = new QueryContext("", false);
        assertEquals("*", queryContext.getQueryString());
        assertNull(queryContext.getDefaultField());

   * The table size is doubled upon further contention until
   * reaching the nearest power of two greater than or equal to the
   * number of CPUS. Table slots remain empty (null) until they are
   * needed.
   *
   * A single spinlock ("busy") is used for initializing and
   * resizing the table, as well as populating slots with new Cells.

/** Encodes HTTP requests and decodes HTTP responses. */
interface ExchangeCodec {
  /** The connection or CONNECT tunnel that owns this codec. */
  val carrier: Carrier

  /** Returns true if the response body and (possibly empty) trailers have been received. */
  val isResponseComplete: Boolean

  /** The socket that carries this exchange. */
  val socket: Socket

  /** Returns an output stream where the request body can be streamed. */

                        }
                    }
                }
                hash = buf.toString();
            } else {
                hash = StringUtil.EMPTY;
            }
        } else {
            hash = StringUtil.EMPTY;
        }

        if (!isFileSystemPath(targetUrl)) {
            return HtmlResponse.fromRedirectPathAsIs(DocumentUtil.encodeUrl(targetUrl + hash));
        }

        assertNull(exception.getMessage());
        assertNull(exception.getCause());
    }

    public void test_constructorWithScheduledJob_emptyToString() {
        // Test with scheduled job that returns empty string from toString
        ScheduledJob scheduledJob = new ScheduledJob() {
            @Override
            public String toString() {
                return "";
            }
        };

  private TestingExecutors() {}

  /**
   * Returns a {@link ScheduledExecutorService} that never executes anything.
   *
   * <p>The {@code shutdownNow} method of the returned executor always returns an empty list despite
   * the fact that everything is still technically awaiting execution. The {@code getDelay} method
   * of any {@link ScheduledFuture} returned by the executor will always return the max long value

        }
    }

    /**
     * Represents an API response for a delete operation.
     */
    public static class ApiDeleteResponse extends ApiResponse {
        /**
         * Constructs an empty ApiDeleteResponse.
         */
        public ApiDeleteResponse() {
            // NOP
        }

        /**
         * The number of deleted items.
         */
        protected long count = 1;

Empty directory for test, see https://golang.org/issues/29837....

            assertEquals(expectedServer, result.getServer());
            // The implementation returns empty strings as empty strings, not null
            assertEquals(expectedShare.isEmpty() ? "" : expectedShare, result.getShare());
            assertEquals(expectedPath.isEmpty() ? "" : expectedPath, result.getPath());
        }