Can't spy on service with multiple methods with the same name

Question

I have a generated Java service via OpenAPI generator, but I have problems to test it:

// @ts-ignore
import { LotInformation } from '../model/lot-information';

// @ts-ignore
import { BASE_PATH, COLLECTION_FORMATS }                     from '../variables';
import { Configuration }                                     from '../configuration';
import {
    LotInformationServiceInterface
} from './lot-information.serviceInterface';



@Injectable({
  providedIn: 'root'
})
export class LotInformationService implements LotInformationServiceInterface {

...

    /**
     * @param lotName 
     * @param observe set whether or not to return the data Observable as the body, response or events. defaults to returning the body.
     * @param reportProgress flag to report request and response progress.
     */
    public apiLotInformationGet(lotName?: string, observe?: 'body', reportProgress?: boolean, options?: {httpHeaderAccept?: 'text/plain' | 'application/json' | 'text/json', context?: HttpContext, transferCache?: boolean}): Observable<LotInformation>;
    public apiLotInformationGet(lotName?: string, observe?: 'response', reportProgress?: boolean, options?: {httpHeaderAccept?: 'text/plain' | 'application/json' | 'text/json', context?: HttpContext, transferCache?: boolean}): Observable<HttpResponse<LotInformation>>;
    public apiLotInformationGet(lotName?: string, observe?: 'events', reportProgress?: boolean, options?: {httpHeaderAccept?: 'text/plain' | 'application/json' | 'text/json', context?: HttpContext, transferCache?: boolean}): Observable<HttpEvent<LotInformation>>;
    public apiLotInformationGet(lotName?: string, observe: any = 'body', reportProgress: boolean = false, options?: {httpHeaderAccept?: 'text/plain' | 'application/json' | 'text/json', context?: HttpContext, transferCache?: boolean}): Observable<any> {

        let localVarQueryParameters = new HttpParams({encoder: this.encoder});
        if (lotName !== undefined && lotName !== null) {
          localVarQueryParameters = this.addToHttpParams(localVarQueryParameters,
            <any>lotName, 'lotName');
        }

        let localVarHeaders = this.defaultHeaders;

        let localVarHttpHeaderAcceptSelected: string | undefined = options && options.httpHeaderAccept;
        if (localVarHttpHeaderAcceptSelected === undefined) {
            // to determine the Accept header
            const httpHeaderAccepts: string[] = [
                'text/plain',
                'application/json',
                'text/json'
            ];
            localVarHttpHeaderAcceptSelected = this.configuration.selectHeaderAccept(httpHeaderAccepts);
        }
        if (localVarHttpHeaderAcceptSelected !== undefined) {
            localVarHeaders = localVarHeaders.set('Accept', localVarHttpHeaderAcceptSelected);
        }

        let localVarHttpContext: HttpContext | undefined = options && options.context;
        if (localVarHttpContext === undefined) {
            localVarHttpContext = new HttpContext();
        }

        let localVarTransferCache: boolean | undefined = options && options.transferCache;
        if (localVarTransferCache === undefined) {
            localVarTransferCache = true;
        }


        let responseType_: 'text' | 'json' | 'blob' = 'json';
        if (localVarHttpHeaderAcceptSelected) {
            if (localVarHttpHeaderAcceptSelected.startsWith('text')) {
                responseType_ = 'text';
            } else if (this.configuration.isJsonMime(localVarHttpHeaderAcceptSelected)) {
                responseType_ = 'json';
            } else {
                responseType_ = 'blob';
            }
        }

        let localVarPath = `/api/lotInformation`;
        return this.httpClient.request<LotInformation>('get', `${this.configuration.basePath}${localVarPath}`,
            {
                context: localVarHttpContext,
                params: localVarQueryParameters,
                responseType: <any>responseType_,
                withCredentials: this.configuration.withCredentials,
                headers: localVarHeaders,
                observe: observe,
                transferCache: localVarTransferCache,
                reportProgress: reportProgress
            }
        );
    }

}

and I will mock this as always:

spyOn(apiService, 'apiLotInformationGet').and.returnValue(of<MockLotInformation>)

But I got the error message:

TS2345: Argument of type Observable<LotInformation> is not assignable to parameter of type Observable<HttpEvent<LotInformation>>
Type LotInformation is not assignable to type HttpEvent<LotInformation>

Is it possible to select a method from these four?