Redux: How to test a connected component?

Question

I am using Enzyme to unit test my React components. I understand that in order to test the raw unconnected component I'd have to just export it and test it (I've done that). I have managed to write a test for the connected component but I am really not sure if this's the right way and also what exactly would I want to test for the connected component.

Container.jsx

import {connect} from 'react-redux';
import Login from './Login.jsx';
import * as loginActions from './login.actions';

const mapStateToProps = state => ({
  auth: state.auth
});
const mapDispatchToProps = dispatch => ({
  loginUser: credentials => dispatch(loginActions.loginUser(credentials))

});
export default connect(mapStateToProps, mapDispatchToProps)(Login);

Container.test.js

import React from 'react';
import {Provider} from 'react-redux';
import {mount, shallow} from 'enzyme';
import {expect} from 'chai';
import LoginContainer from '../../src/login/login.container';
import Login from '../../src/login/Login';


describe('Container Login', () => {
  it('should render the container component', () => {
    const storeFake = state => ({
      default: () => {
      },
      subscribe: () => {
      },
      dispatch: () => {
      },
      getState: () => ({ ...state })
    });
    const store = storeFake({
      auth: {
        sport: 'BASKETBALL'
      }
    });

    const wrapper = mount(
      <Provider store={store}>
        <LoginContainer />
      </Provider>
    );

    expect(wrapper.find(LoginContainer).length).to.equal(1);
    const container = wrapper.find(LoginContainer);
    expect(container.find(Login).length).to.equal(1);
    expect(container.find(Login).props().auth).to.eql({ sport: 'BASKETBALL' });
  });
});

Answer 1

If we have a router issue, we can consider to add the router lib into the test file, eg:

import React from 'react';
import { Provider } from 'react-redux';
import { BrowserRouter as Router } from 'react-router-dom';
import { mount } from 'enzyme';
import ReadDots from './ReadDots';

const storeFake = state => ({
  default: () => {
  },
  subscribe: () => {
  },
  dispatch: () => {
  },
  getState: () => ({ ...state })
});

const store = storeFake({
  dot: {
    dots: [
      {
        id: '1',
        dot: 'test data',
        cost: '100',
        tag: 'pocket money'
      }
    ]
  }
});

describe('<ReadDots />', () => {
  it('should render ReadDots component', () => {
    const component = mount(
      <Provider store={store}>
        <Router>
          <ReadDots />
        </Router>
      </Provider>
    );
    expect(component.length).toEqual(1);
  });
});

Answer 2

As you pointed out, the way I usually do this is to export the un-connected component as well, and test that.

i.e.

export {Login};

Here's an example. Source of the component, and source of the tests.

For the wrapped component, I don't author tests for those because my mappings (mapStateToProps and mapDispatchToProps) are generally very simple. If I wanted to test a wrapped component, I'd really just be testing those maps. So those are what I would choose to explicitly test, rather than re-testing the entire component in a wrapped form.

There are two ways to test those functions. One way would be to export the functions within the module itself.

i.e.;

export {mapStateToProps, mapDispatchToProps}

I'm not a huge fan of this, because I wouldn't want other modules in the app to access them. In my tests, I sometimes use babel-plugin-rewire to access "in-scope" variables, so that's what I would do in this situation.

That might look something like:

import {
  Login, __Rewire__
}

const mapStateToProps = __Rewire__.__get__('mapStateToProps');

describe('mapStateToProps', () => { ... });

Answer 3

This is an interesting question.

I usually do import both container and component to do the testing. For container testing I use, redux-mock-store. Component testing is for testing async functions. For instance in your case, login process is an async function using sinon stubs. Here is a snippet of the same,

import React from 'react';
import {Provider} from 'react-redux';
import {mount, shallow} from 'enzyme';
import {expect} from 'chai';
import LoginContainer from '../../src/login/login.container';
import Login from '../../src/login/Login';
import configureMockStore from 'redux-mock-store';
import thunk from 'redux-thunk';
import { stub } from 'sinon';

const mockStore = configureMockStore([thunk]);

describe('Container Login', () => {
  let store;
  beforeEach(() => {
    store = mockStore({
      auth: {
        sport: 'BASKETBALL',
      },
    });
  });
  it('should render the container component', () => {
    const wrapper = mount(
      <Provider store={store}>
        <LoginContainer />
      </Provider>
    );

    expect(wrapper.find(LoginContainer).length).to.equal(1);
    const container = wrapper.find(LoginContainer);
    expect(container.find(Login).length).to.equal(1);
    expect(container.find(Login).props().auth).to.eql({ sport: 'BASKETBALL' });
  });

  it('should perform login', () => {
    const loginStub = stub().withArgs({
      username: 'abcd',
      password: '1234',
    });
    const wrapper = mount(<Login
      loginUser={loginStub}
    />);
  wrapper.find('button').simulate('click');
  expect(loginStub.callCount).to.equal(1);
  });
});