ember testing Error Adapter operation failed

My test is pretty simple. It was working before but now I have facing a new issue I am getting failure message

Adapter operation failed

at http://localhost:4200/assets/test-support.js:4578:13 at exports.default._emberTestingAdaptersAdapter.default.extend.exception (http://localhost:4200/assets/vendor.js:52460:34) at onerrorDefault (http://localhost:4200/assets/vendor.js:43162:24) at Object.exports.default.trigger (http://localhost:4200/assets/vendor.js:67346:11) at Promise._onerror (http://localhost:4200/assets/vendor.js:68312:22) at publishRejection (http://localhost:4200/assets/vendor.js:66619:15)

TEST

test('test characters', function(assert) {
  server.create('character',{name: "Telly Tubby"});
  visit('/characters');
  fillIn('.search',"Telly Tubby");
  click('#search-btn');
  andThen(function() {  
    var results = find('.character-item');
    assert.equal(results.length,1);
  });
});

I dont remember doing anything fancy. I am not sure what is breaking.

yes my start-app.js helper is pretty standard

I went through the document and i feel it has something to do with Ember.Test.Adapter set to QunitAdapter by default.

import Ember from 'ember';
import Application from '../../app';
import config from '../../config/environment';
// import initializeTestHelpers from 'simple-auth-testing/test-helpers';
// initializeTestHelpers();

export default function startApp(attrs) {
  var application;

  var attributes = Ember.merge({}, config.APP);
  attributes = Ember.merge(attributes, attrs); // use defaults, but you can override;

  Ember.run(function() {
    application = Application.create(attributes);
    application.setupForTesting();
    application.injectTestHelpers();
  });

  return application;
}

I am not sure how to fix this. the tests are passing though