Jasmine Spy not working with TestScheduler (I could use some help :-)

[antonkarsten]

I am writing a test for a service using TestSchedular and eventhough it is quite clear that my spy has been called, when i try to assert it it fails. I guess I am doing something wrong in the ordering or the way I write the test. Does anyone have an idea?

I have made a simplified version of my service and test. You can try it out at :
https://stackblitz.com/edit/typescript-6sqw4w?file=test.ts

import { BehaviorSubject, Observable } from "rxjs";
import { scan, switchMap } from "rxjs/operators";
import { TestScheduler } from "rxjs/testing";

interface TransformService {
  transform: (item: string) => Observable<string>;
}

class MyService {
  items = new BehaviorSubject<string>(null);

  constructor(private readonly transformService: TransformService) {}

  addItem(item: string) {
    this.items.next(item);
  }

  tranform(item: string) {
    return this.transformService.transform(item);
  }

  getItems() {
    return this.items.asObservable().pipe(
      switchMap((item) => {
        return this.tranform(item);
      }),
      scan((accumalation, item) => {
        accumalation.push(item);
        return [...accumalation];
      }, [])
    );
  }
}

/**
 * Test written with Jasmine Marbles
 */
describe("Main", () => {
  let testScheduler;
  let transformServiceSpy;

  beforeEach(() => {
    testScheduler = new TestScheduler((actual, expected) => {
      expect(actual).toEqual(expected);
    });

    transformServiceSpy = jasmine.createSpyObj("TransformService", [
      "transform",
    ]);
  });

  it("should transform the string", () => {
    testScheduler.run((helpers) => {
      const { cold, expectObservable } = helpers;
      const transformResponse = cold("5000ms a", {
        a: "transformed",
      });
      transformServiceSpy.transform.and.returnValue(transformResponse);

      const service = new MyService(transformServiceSpy);

      const expected = "5000ms a";
      const values = {
        a: ["hello"],
      };
      expectObservable(service.getItems()).toBe(expected, values);
      service.addItem("transformed");
      expect(transformServiceSpy.transform).toHaveBeenCalledTimes(1);
    });
  });
});

when I remove the following line it works

expect(transformServiceSpy.transform).toHaveBeenCalledTimes(1);

thank you very much !!
Anton

[cartant]

Read about flush and call it before you make that assertion:

flush();
expect(transformServiceSpy.transform).toHaveBeenCalledTimes(1);

[antonkarsten]

I had actually read about flush and I had tried it in my real world (more complex) code. The problem was that I used it the wrong way. Than I thought that it wasnt the solution to my problem and when I created the simple version that I posted above I didnt try it again. my mistake.

After your answer I got it working straight away :-) Thank you very much.