@Override
  public boolean isStarted() {
    // return _server.isStarted();
    return false;
  }
Extend the base ServletTester class with a couple of helper methods. This depends on a patched
ServletTester class which exposes the _server variable as package-private.
extensions/geode-modules-session/src/integrationTest/java/org/apache/geode/modules/session/internal/filter/MyServletTester.java