t('we give an error with useful details', function() {
          ajax.url = '/responds_to_get_with_502_error_json';
          ajax.handleAs = 'json';
          var eventFired = false;
          ajax.addEventListener('error', function(event) {
            expect(event.detail.request).to.be.ok;
            expect(event.detail.error).to.be.ok;
            eventFired = true;
          });
          var request = ajax.generateRequest();
          var promise = request.completes.then(function() {
            thro