Stackoverflow Answer : 40769051

controllers.application.js

import Ember from 'ember';
import EmberValidations from 'ember-validations';

export default Ember.Controller.extend(EmberValidations,{
  appName: 'Ember Twiddle',
  user: {name: 'Jack'},
  validationActive: false,
  
  validations: {
    'user.name': {
      length: { minimum: 5, 'if':'validationActive' }
    }
  },

  actions: {
    toggleValidation: function() {
      this.toggleProperty("validationActive");
    }
  }

});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
{{input value=(mut (get user 'name'))}}

<br>
Is validation active: {{validationActive}} 
<br>
Validation Result is: {{isValid}}
<br>
<button {{action "toggleValidation"}}>Toggle Validation</button>
<br>

tests.helpers.destroy-app.js

import Ember from 'ember';

export default function destroyApp(application) {
  Ember.run(application, 'destroy');
}

tests.helpers.resolver.js

import Resolver from '../../resolver';
import config from '../../config/environment';

const resolver = Resolver.create();

resolver.namespace = {
  modulePrefix: config.modulePrefix,
  podModulePrefix: config.podModulePrefix
};

export default resolver;

tests.helpers.start-app.js

import Ember from 'ember';
import Application from '../../app';
import config from '../../config/environment';

const { run } = Ember;
const assign = Ember.assign || Ember.merge;

export default function startApp(attrs) {
  let application;

  let attributes = assign({rootElement: "#test-root"}, config.APP);
  attributes = assign(attributes, attrs); // use defaults, but you can override;

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

  return application;
}

tests.test-helper.js

import resolver from './helpers/resolver';
import {
  setResolver
} from 'ember-qunit';

setResolver(resolver);

twiddle.json

{
  "version": "0.10.6",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.9.0",
    "ember-data": "2.9.0",
    "ember-template-compiler": "2.9.0",
    "ember-testing": "2.9.0"
  },
  "addons": {
    "ember-validations": "2.0.0-alpha.5"
  }
}