Angular2 testing service -- undefined service

Question

Hi I am trying to write unit tests for my service following this procedure: https://developers.livechatinc.com/blog/testing-angular-2-apps-dependency-injection-and-components/ but I keep getting an error.

Here is the service test

import {it,inject,injectAsync,beforeEachProviders,TestComponentBuilder} from 'angular2/testing';
import {CORE_DIRECTIVES,FORM_DIRECTIVES,FormBuilder,ControlGroup,Validators,AbstractControl} from 'angular2/common';
import {KibanaDataServices} from "./kibana-data-services";
import {Http,Response,Headers, HTTP_PROVIDERS, ConnectionBackend} from 'angular2/http';
declare let $:JQueryStatic;

describe('KibanaDataServices', () => {
  beforeEach(function() {
  this.kibanaDataServices = new KibanaDataServices()

});


it("date properly formats for trends view",function(){
    // logs as {}
    console.log("this is " + JSON.stringify(this));
    // logs as undefined
    console.log("this.kibanaDataServices is " + this.kibanaDataServices);

    let dateQuery: string = this.kibanaDataServices.formulateQueryDates("7d");
    expect(dateQuery).toEqual("(from:'now-7d',mode:quick,to:'now'))");
});

});

And the console.log for this is an empty object, and this.kibanaDataServices is simply undefined. The path I am specifying is correct as kibana-data-services and kibana-data-services.spec.ts (this test file) are in the same folder so I am not sure what is wrong.

The error I get specifically is:

 TypeError: Attempted to assign to readonly property. in /Users/project/config/spec-bundle.js (line 42836)
TypeError: undefined is not an object (evaluating 'this.kibanaDataServices.formulateQueryDates') in /Users/project/config/spec-bundle.js (line 42841)

UPDATE: Not using "this" leads to an error of not defined in the "it" statement

describe('KibanaDataServices', () => {

  beforeEach(function() {
  kibanaDataServices = new KibanaDataServices()

  });


  it("date properly formats for trends view",function(){
    console.log("kibanaDataServices is " + kibanaDataServices);

      let dateQuery: string = kibanaDataServices.formulateQueryDates("7d");
      expect(dateQuery).toEqual("(from:'now-7d',mode:quick,to:'now'))");
  });

});

Answer 1

Don't use this this.kibanaDataServices. Just create a local variable

let kibanaDataServices;

beforeEach(() => {
  kibanaDataServices = new KibanaDataServices()
});

And get rid of all your this when referencing kibanaDataServices