protected void checkDepth(SimulatedArchivalUnit sau) {
   log.debug("checkDepth()");
   String URL_ROOT = sau.getUrlRoot();
   assertEquals(0, sau.getLinkDepth(URL_ROOT + "/index.html"));
   assertEquals(0, sau.getLinkDepth(URL_ROOT + "/"));
   assertEquals(1, sau.getLinkDepth(URL_ROOT + "/001file.html"));
   assertEquals(1, sau.getLinkDepth(URL_ROOT + "/branch1/index.html"));
   assertEquals(1, sau.getLinkDepth(URL_ROOT + "/branch1/"));
   assertEquals(2, sau.getLinkDepth(URL_ROOT + "/branch1/001file.html"));
 }