title: How to write test case to call a method inside a "router navigation end subscribe"?
body: <p>I am creating some breadcrumbs based on router events.
  I have created a router test bed with navigationEnd and mock router but not working. Not understanding how to call my methods inside the subscribe and how to write the test case for this to call these methods</p>
  
  <pre><code>ngOnInit() {
  this.router.events.pipe(filter(e instance of NavigationEnd)).subscribe( event =&gt; {
  // calling this method 
  this.callmethod();
  // Initiating my breadcrumb method by passing the event
  this.initiateBreadcrumb(event);
  });
  </code></pre>