How to mock Angular 4.3 httpClient an error response in testing

I have a below interceptor auth-interceptor.service.ts

import {Injectable, Injector} from '@angular/core';
import {HttpErrorResponse, HttpEvent, HttpHandler, HttpInterceptor, HttpRequest} from '@angular/common/http';
import {Observable} from 'rxjs/Observable';
import {Cookie} from './cookie.service';
import {Router} from '@angular/router';
import {UserService} from './user.service';
import {ToasterService} from '../toaster/toaster.service';
import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/throw';

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
    constructor(private injector: Injector) {}

    private handleError(err: HttpErrorResponse): Observable<any> {
        let errorMsg;
        if (err.error instanceof Error) {
            // A client-side or network error occurred. Handle it accordingly.
            errorMsg = `An error occurred: ${err.error.message}`;
        } else {
            // The backend returned an unsuccessful response code.
            // The response body may contain clues as to what went wrong,
            errorMsg = `Backend returned code ${err.status}, body was: ${err.error}`;
        }
        if (err.status === 401 || err.status === 403) {
            this.injector.get(UserService).purgeAuth();
            this.injector.get(ToasterService).showError(`Unauthorized`, errorMsg);
            this.injector.get(Router).navigateByUrl(`/login`);
        }
        console.error(errorMsg);
        return Observable.throw(errorMsg);
    }

    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        // Clone the request to add the new header.
        const authReq = req.clone({headers: req.headers.set(Cookie.tokenKey, Cookie.getToken())});
        // Pass on the cloned request instead of the original request.
        return next.handle(authReq).catch(err => this.handleError(err));
    }
}

Now I am trying to mock the http.get to throw the error, so that method handleError consoles the error message.

Below is my approach to the test case auth-interceptor.service.specs.ts

import {async, inject, TestBed} from '@angular/core/testing';

import {AuthInterceptor} from './auth-interceptor.service';
import {ApiService} from './api.service';
import {HttpClientTestingModule, HttpTestingController} from '@angular/common/http/testing';
import {environment} from '../../../environments/environment';

describe(`AuthInterceptor`, () => {
    const somePath = `/somePath`;

    beforeEach(() => {
        TestBed.configureTestingModule({
            imports: [HttpClientTestingModule],
            providers: [AuthInterceptor, ApiService]
        });
    });

    it(`should be created`, inject([AuthInterceptor], (service: AuthInterceptor) => {
        expect(service).toBeTruthy();
    }));


    it(`should log an error to the console on error on get()`, async(inject([ApiService, HttpTestingController],
        (apiService: ApiService, httpMock: HttpTestingController) => {
            spyOn(console, 'error');
            apiService.get(somePath).subscribe((res) => {
                console.log(`in success:`, res);
            }, (error) => {
                console.log(`in error:`, error);
            });

            const req = httpMock.expectOne(`${environment.apiUri}${somePath}`);
            req.flush({
                type: 'ERROR',
                status: 404,
                body: JSON.stringify({color: `blue`})
            });
            expect(console.error).toHaveBeenCalled();
        }))
    );
});

When flushing the response, I am not sure how to flush a error response, so that the method handleError will be called in my interceptor and that eventually calls console.error. Documentation doesn't have any example to my situation. Any help or suggestion is appreciated.