I had the same problem recently. It was caused by a call to router.navigate inside the ngOnInit method of a component. The test was trying to create the component, but inside ngOnInit it was attempting to navigate away from the component (because certain conditions were not met).
In my case, I am importing the RouterTestingModule as part of TestBed.configureTestingModule. So to fix this I simply registered a route with RouterTestingModule. For example, suppose your navigation call looks like router.navigate(['example']) and it resolves to ExampleComponent. You can set up the test as follows:
RouterTestingModule.withRoutes([
{ path: 'example', component: ExampleComponent}
])
Doing the above allowed my tests to run without issuing Cannot match any routes errors.
For what it’s worth, I think a better way would be to stub the router and just confirm that appropriate calls to navigate are made.