How to test canActivate with karma + jasmine in angular 2?

Angular 2 v.2.0.0 - TS + karma + jasmine.

I would test this canActivate function:

    public canActivate(next: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<boolean> {
    return this.serverThisLogin.checkAuth().map((e: boolean) => {
        if (e) {
            return true;
        }
    }). catch(() => {
        this.router.navigate(["/login"]);
        return Observable.of(false);
    });
}

How implement this? When i add this construction

    beforeEach(() => {
        canAct = new CanActivate(null, null);
    });

i've got this error 'CanActivate' only refers to a type, but is being used as a value here.