Angular 6 Unit Tests: An error was thrown in afterAll\nReferenceError: Can't find variable: $ thrown

Question

When running my unit tests, from time to time, even if they pass, at the end of all the tests running, I will get the following error.

On my Jenkins CI build running

Answer 1

In my case changing the import from Observable to Rx Library has fixed the issue

before:

import { Observable } from 'rxjs/Observable';

After:

import { Observable } from 'rxjs/Rx';