ApolloTestingController doesn't seem to be triggering an HttpInterceptor

[KarmaCop213]

Describe the bug

ApolloTestingController doesn't seem to be triggering an HttpInterceptor I have

To Reproduce

I have an HttpInterceptor declared like so:

export class ErrorHandlerInterceptor implements HttpInterceptor {

and I have call on my code to apollo like this:

import { Apollo } from "apollo-angular"
(...)
constructor(private readonly apollo: Apollo) {}
(...)
return this.apollo.mutate<T>({ mutation, variables })

on my test I make a call to this.apollo.mutate<T>({ mutation, variables }).
And to simulate the call, the only way I could find that triggers the HttpInterceptor is to make a dummy call to an endpoint using HttpClient:

const apolloTestingController = TestBed.inject(ApolloTestingController),
const httpMock  = TestBed.inject(HttpTestingController),
const httpClient  = TestBed.inject(HttpClient)

this.apolloTestingController.expectOne(callingGraphqlQuery).flush(responseBody as unknown)
this.apolloTestingController.verify()

this.httpClient.post("/graphql", { operationName }).subscribe()
this.httpMock.expectOne({ method: "POST" }).flush(responseBody, opts)
this.httpMock.verify()

Expected behavior

From my point of view ApolloTestingController should trigger HttpInterceptor.

Environment:

├── @angular/[email protected]
├── @angular/[email protected]
├── @apollo/[email protected]
├── [email protected]
├── [email protected]
└── [email protected]