jest test a saga

sagas.test.ts

describe("updateFooSaga", () => {
    afterEach(() => {
      global.fetch = jest.fn().mockReset();
    });
    const gen = updateFooSaga(updateFoo(mockFoo));
    it("should handle successful fetch request", () => {
      global.fetch = jest.fn().mockResolvedValueOnce({
        ok: true,
        json: () => Promise.resolve(mockSuccessResponse),
      });
      gen.next(); // fetch call
      expect(gen.next().value).toEqual(put(updateFooSuccess()));
    });
    it("should handle failed fetch request", () => {
      global.fetch = jest
        .fn()
        .mockRejectedValueOnce(() => Promise.reject("nope"));
      try {
        gen.next().value; // fetch call
      } catch (error) {
        expect(gen.next().value).toEqual(put(updateFooError()));
      }
    });
  });

sagas.ts

export function* updateFooSaga({ payload }: PayloadAction<FooList>) {
  try {
    yield fetch(
      "https://foobar.com",
      {
        method: "POST",
        headers: {
          "Content-Type": "application/json",
        },
        mode: "cors",
        body: JSON.stringify(payload),
      }
    );
    yield put(updateFooSuccess());
  } catch (error) {
    yield put(updateFooError());
  }
}

export function* watchUpdateFoo() {
  yield takeLatest(updateFoo.toString(), updateFooSaga);
}