anchor.diff:                </div>
               </div>"""));
   
  -          var grp = te.query('#${safeGroup}');
  +          // 'safeGroup' could be empty
  +          var grp = (safeGroup == '') ? null : te.query('#${safeGroup}');
             if (grp != null){
               grp.on.click.add((_){
                 var row = document.query('.unittest-row-${safeGroup}');
  
positive.code:           var groupTestPassedCount = testsInGroup.filter(
                (TestCase t) => t.result == 'pass').length;
            groupPassFail = groupTotalTestCount == groupTestPassedCount;
  
            te.elements.add(new Element.html("""
              <div>
  
negative.code:                    class='unittest-group ${safeGroup} test${safeGroup}'>
                  <div ${_isIE ? "style='display:inline-block' ": ""}
                       class='unittest-row-status'>
                    <div class='$passFailClass'></div>
                  </div>
                  <div ${_isIE ? "style='display:inline-block' ": ""}>
                      ${test_.currentGroup}</div>
  