Test redux actions that calls an API

Question

What is the best way to test this function

export function receivingItems() {
  return (dispatch, getState) => {
    axios.get('/api/items')
      .then(function(response) {
        dispatch(receivedItems(response.data));
      });
  };
}

this is currently what I have

describe('Items Action Creator', () => {
  it('should create a receiving items function', () => {
    expect(receivingItems()).to.be.a.function;
  });
});

Answer 1

I solved this in a different way: injecting axios as a dependency of action. I prefer this approach over 'rewiring' dependencies.

So I used the same approach of testing redux-connected components. When I export actions I export two versions: one with (to be used for components) and one without (for testing) binding dependencies.

Here is how my actions.js file looks like:

import axios from 'axios'

export const loadDataRequest = () => {
  return {
    type: 'LOAD_DATA_REQUEST'
  }
}
export const loadDataError = () => {
  return {
    type: 'LOAD_DATA_ERROR'
  }
}
export const loadDataSuccess = (data) =>{
  return {
    type: 'LOAD_DATA_SUCCESS',
    data
  }
}
export const loadData = (axios) => {
  return dispatch => {
    dispatch(loadDataRequest())
    axios
      .get('http://httpbin.org/ip')
      .then(({data})=> dispatch(loadDataSuccess(data)))
      .catch(()=> dispatch(loadDataError()))
  }
}
export default {
  loadData: loadData.bind(null, axios)
}

Then testing with jest (actions.test.js):

import { loadData } from './actions'

describe('testing loadData', ()=>{
  test('loadData with success', (done)=>{

    const get = jest.fn()
    const data = {
      mydata: { test: 1 }
    }
    get.mockReturnValue(Promise.resolve({data}))

    let callNumber = 0
    const dispatch = jest.fn(params =>{
      if (callNumber===0){
        expect(params).toEqual({ type: 'LOAD_DATA_REQUEST' })
      }
      if (callNumber===1){
        expect(params).toEqual({
          type: 'LOAD_DATA_SUCCESS',
          data: data
        })
        done()
      }
      callNumber++
    })
    const axiosMock = {
      get
    }
    loadData(axiosMock)(dispatch)
  })
})

When using the actions inside a component I import everything:

import Actions from './actions'

And to dispatch:

Actions.loadData() // this is the version with axios binded.

Answer 2

From Redux “Writing Tests” recipe:

For async action creators using Redux Thunk or other middleware, it’s best to completely mock the Redux store for tests. You can still use applyMiddleware() with a mock store, as shown below (you can find the following code in redux-mock-store). You can also use nock to mock the HTTP requests.

function fetchTodosRequest() {
  return {
    type: FETCH_TODOS_REQUEST
  }
}

function fetchTodosSuccess(body) {
  return {
    type: FETCH_TODOS_SUCCESS,
    body
  }
}

function fetchTodosFailure(ex) {
  return {
    type: FETCH_TODOS_FAILURE,
    ex
  }
}

export function fetchTodos() {
  return dispatch => {
    dispatch(fetchTodosRequest())
    return fetch('http://example.com/todos')
      .then(res => res.json())
      .then(json => dispatch(fetchTodosSuccess(json.body)))
      .catch(ex => dispatch(fetchTodosFailure(ex)))
  }
}

can be tested like:

import expect from 'expect'
import { applyMiddleware } from 'redux'
import thunk from 'redux-thunk'
import * as actions from '../../actions/counter'
import * as types from '../../constants/ActionTypes'
import nock from 'nock'

const middlewares = [ thunk ]

/**
 * Creates a mock of Redux store with middleware.
 */
function mockStore(getState, expectedActions, done) {
  if (!Array.isArray(expectedActions)) {
    throw new Error('expectedActions should be an array of expected actions.')
  }
  if (typeof done !== 'undefined' && typeof done !== 'function') {
    throw new Error('done should either be undefined or function.')
  }

  function mockStoreWithoutMiddleware() {
    return {
      getState() {
        return typeof getState === 'function' ?
          getState() :
          getState
      },

      dispatch(action) {
        const expectedAction = expectedActions.shift()

        try {
          expect(action).toEqual(expectedAction)
          if (done && !expectedActions.length) {
            done()
          }
          return action
        } catch (e) {
          done(e)
        }
      }
    }
  }

  const mockStoreWithMiddleware = applyMiddleware(
    ...middlewares
  )(mockStoreWithoutMiddleware)

  return mockStoreWithMiddleware()
}

describe('async actions', () => {
  afterEach(() => {
    nock.cleanAll()
  })

  it('creates FETCH_TODOS_SUCCESS when fetching todos has been done', (done) => {
    nock('http://example.com/')
      .get('/todos')
      .reply(200, { todos: ['do something'] })

    const expectedActions = [
      { type: types.FETCH_TODOS_REQUEST },
      { type: types.FETCH_TODOS_SUCCESS, body: { todos: ['do something']  } }
    ]
    const store = mockStore({ todos: [] }, expectedActions, done)
    store.dispatch(actions.fetchTodos())
  })
})

Answer 3

I would use a stub axios (for example by using mock-require) and write a test that actually calls receivingItems()(dispatch, getState) and makes sure dispatch is called with the correct data.