I want to test the error part of the http call in the myService.ts file.

private executeSend(id: string): void {
  this.conService.createContact(id).subscribe(resp => {
    // some coding
  },
  err => { // need for unit test
    if(err.status === 504) {
      // some coding
    }
  });
}

I wrote the unit testing as like below but it shows me: Cannot read properties of undefined (reading 'createContact')

it('should check 504 error for executeSend method', () => {
    const errorResponse = new Response("err", {
      status: 504
    });
    const fetchSpy = jasmine.createSpy('post').and.returnValue(errorResponse);
    const op = new service['myService']['createContact'](fetchSpy);
 
    let error;
    try {
      op.createContact()
    } catch (e) {
      error = e;
    }
    expect(error).toEqual(new Error('err'));
    expect(fetchSpy).toHaveBeenCalled();
  });