How can I test an infinite loop in a generator?

Background

I'm trying to write a saga to handle polling when a certain view is open, and I want to cancel the polling when the view is closed. This is pretty much the textbook example from the docs! In the course of writing a test for it, I ran into the following problem.

Problem

When I introduce a delay and try to mock it with a fake timer, the generator does not yield on the second loop and the test fails. However, the code will log loop 0 and loop 1, so I know it is entering the loop a second time.

If I use a real delay, the test passes!

Is this expected? Am I losing my mind?

import { runSaga } from "redux-saga";
import { call, delay } from "redux-saga/effects";
import sinon from "sinon";

describe("faking the delay", () => {
  it("should loop more than once", async () => {
    let i = 0;
    const clock = sinon.useFakeTimers();
    const spy = jest.fn().mockReturnValue(true);
    function* loop() {
      while (true) {
        console.log("loop %d", i);
        yield call(spy);
        // yield delay(1);
        yield new Promise(resolve => setTimeout(resolve, 1));
        i++;
      }
    }

    await runSaga({}, loop, spy);
    expect(spy).toBeCalledTimes(1);

    // await new Promise(resolve => setTimeout(resolve, 1));

    clock.tick(1)
    clock.tick(1)

    expect(spy).toBeCalledTimes(2); // FAILS

    clock.restore();
  });
});