Unit testing an observable in Angular 2

Question

What is the correct way of unit testing a service returning an Observable result in Angular 2? Let\'s say we have a getCars method in a CarService service class:

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Answer 1

AsyncTestCompleter is deprecated https://github.com/angular/angular/issues/5443. injectAsync replaced it https://github.com/angular/angular/issues/4715#issuecomment-149288405
but injectAsync is now also deprecated
injectAsync is not deprecated anymore https://github.com/angular/angular/pull/5721 (see also comment from @ErdincGuzel)

it('retrieves all the cars', injectAsync( [CarService], ( carService ) => {
     var c = PromiseWrapper.completer();
     carService.getCars().subscribe( result => {         
         expect(result.length).toBeGreaterThan(0);
         c.resolve();
     } ); 
     return c.promise;      
}) );