@Override
  public void start() {
    MasterServletFilter masterServletFilter = MasterServletFilter.getInstance();
    if (masterServletFilter != null) {
      // Probably a database upgrade. MasterSlaveFilter was instantiated by the servlet container
      // while spring was not completely up.
      // See https://jira.sonarsource.com/browse/SONAR-3612
      masterServletFilter.initHttpFilters(Arrays.asList(httpFilters));
      masterServletFilter.initServletFilters(Arrays.asList(servletFilters));
    }
  }
@Test
  public void should_not_fail_if_master_filter_is_not_up() {
    MasterServletFilter.setInstance(null);
    new RegisterServletFilters(new ServletFilter[2], new HttpFilter[2]).start();
  }