Exposed Effects

The Promise returned by the run method resolves with an object that contains any effects yielded by your saga and sagas that it forked. You can use this for finer-grained control over testing exact number of effects. Be careful when testing top-level sagas that fork other sagas because the effects object will include yielded effects from all forked sagas too. There currently is no way to distinguish between effects yielded by the top-level saga and forked sagas.

function* userSaga(id) {
  const user = yield call(fetchUser, id);
  const pet = yield call(fetchPet, user.petId);

  yield put({ type: 'DONE', payload: { user, pet } });
}

it('exposes effects', () => {
  const id = 42;
  const petId = 20;

  const user = { id, petId, name: 'Jeremy' };
  const pet = { name: 'Tucker' };

  return expectSaga(saga, id)
    .provide([
      [call(fetchUser, id), user],
      [call(fetchPet, petId), pet],
    ])
    .run()
    .then((result) => {
      const { effects } = result;

      expect(effects.call).toHaveLength(2);
      expect(effects.put).toHaveLength(1);

      expect(effects.call[0]).toEqual(call(fetchUser, id));
      expect(effects.call[1]).toEqual(call(fetchPet, petId));

      expect(effects.put[0]).toEqual(
        put({ type: 'DONE', payload: { user, pet } })
      );
    });
});

Of course, async functions work nicely with this feature too.

it('exposes effects using async functions', async () => {
  const id = 42;
  const petId = 20;

  const user = { id, petId, name: 'Jeremy' };
  const pet = { name: 'Tucker' };

  const { effects } = await expectSaga(saga, id)
    .provide([
      [call(fetchUser, id), user],
      [call(fetchPet, petId), pet],
    ])
    .run();

  expect(effects.call).toHaveLength(2);
  expect(effects.put).toHaveLength(1);

  expect(effects.call[0]).toEqual(call(fetchUser, id));
  expect(effects.call[1]).toEqual(call(fetchPet, petId));

  expect(effects.put[0]).toEqual(
    put({ type: 'DONE', payload: { user, pet } })
  );
});

Inspect Specific Properties

If you want to inspect specific properties on an effect, you can use the asEffect util from Redux Saga.

import { asEffect } from 'redux-saga/utils';

it('can test properties on effects', () => {
  const id = 42;
  const petId = 20;

  const user = { id, petId, name: 'Jeremy' };
  const pet = { name: 'Tucker' };

  return expectSaga(saga, id)
    .provide([
      [call(fetchUser, id), user],
      [call(fetchPet, petId), pet],
    ])
    .run()
    .then((result) => {
      const { effects } = result;

      const fetchUserCall = asEffect.call(effects.call[0]);

      expect(fetchUserCall.fn).toBe(fetchUser);
      expect(fetchUserCall.args).toEqual([42]);
    });
});

All Effects

If you want all the effects consolidated in the order they were yielded, you can use the allEffects property from the resolved object.

function* saga() {
  yield call(identity, 42);
  yield put({ type: 'HELLO' });
}

it('exposes all yielded effects in order', () => {
  return expectSaga(saga)
    .run()
    .then((result) => {
      const { allEffects } = result;

      expect(allEffects).toEqual([
        call(identity, 42),
        put({ type: 'HELLO' }),
      ]);
    });
});

Available Effects

The available effects are:

• actionChannel
• call
• cps
• fork
• getContext
• join
• put
• race
• select
• setContext
• take