How do you test a generator function in Redux-Saga

Question

With the help of code can i know How do you test a generator function in Redux-Saga?

Answer 1

Testing a saga means manually stepping through the generator function and asserting that it yields the expected effects in order.

1. Sample Saga to Test

import { call, put } from 'redux-saga/effects';

import { fetchDataApi } from './api';

function* fetchDataSaga(action) {

  try {

    const data = yield call(fetchDataApi, action.payload);

    yield put({ type: 'FETCH_SUCCESS', payload: data });

  } catch (error) {

    yield put({ type: 'FETCH_FAILURE', error: error.message });

  }

}

2. Test Using Jest

import { call, put } from 'redux-saga/effects';

import { fetchDataSaga } from './sagas';

import { fetchDataApi } from './api';

describe('fetchDataSaga', () => {

  const action = { type: 'FETCH_REQUEST', payload: 1 };

  const generator = fetchDataSaga(action);

  it('should call fetchDataApi with correct payload', () => {

    expect(generator.next().value).toEqual(call(fetchDataApi, 1));

  });

  it('should dispatch FETCH_SUCCESS on success', () => {

    const mockResponse = { name: 'Test' };

    expect(generator.next(mockResponse).value).toEqual(

      put({ type: 'FETCH_SUCCESS', payload: mockResponse })

    );

  });

  it('should handle errors with FETCH_FAILURE', () => {

    const errorGen = fetchDataSaga(action);

    errorGen.next(); // skip to call

    const error = new Error('API failed');

    expect(errorGen.throw(error).value).toEqual(

      put({ type: 'FETCH_FAILURE', error: 'API failed' })

    );

  });

});