Ember 2.12 to Ember 2.13 -- Issue around rename of router to _routerMicrolib

I am an Ember newbie. Working on migration of project from Ember 2.11 to 2.15.

After migrating from 2.12 to 2.13, I am running into this issue related to a deprecation of router renamed to _routerMicrolib (https://emberjs.com/deprecations/v2.x/#toc_ember-router-router-renamed-to-ember-router-_routermicrolib), when I ran the route unit tests.

1. Issue calling a router refresh

this.get('router').refresh(), gives:

undefined is not a constructor (evaluating 'route.get('router').refresh()')

this.router.refresh:

undefined is not an object (evaluating 'this.router._routerMicrolib.refresh')

2. Issue calling route.get('router').transitionTo

route.transitionTo:

undefined is not an object (evaluating 'this.router._routerMicrolib.get')

route.get('router').transitionTo:

undefined is not a constructor (evaluating 'route.get('router').refresh()')

Anyone has an idea how to call refresh, and get in these scenarios?