addCallback(f, callback, directExecutor());
  }

  private class CountingSameThreadExecutor implements Executor {
    int runCount = 0;

    @Override
    public void execute(Runnable command) {
      command.run();
      runCount++;
    }
  }

  private final class MockCallback implements FutureCallback<String> {
    @Nullable private String value = null;
    @Nullable private Throwable failure = null;

   * to the string returned by {@link #serviceName}
   */
  protected Executor executor() {
    return command -> MoreExecutors.newThread(serviceName(), command).start();
  }

  @Override
  public String toString() {
    return serviceName() + " [" + state() + "]";
  }

  @Override
  public final boolean isRunning() {

/**
 * A specification of a {@link CacheBuilder} configuration.
 *
 * <p>{@code CacheBuilderSpec} supports parsing configuration off of a string, which makes it
 * especially useful for command-line configuration of a {@code CacheBuilder}.
 *
 * <p>The string syntax is a series of comma-separated keys or key-value pairs, each corresponding
 * to a {@code CacheBuilder} method.
 *
 * <ul>