Redux: How to test a connected component? - unit-testing

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

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);
});
});

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

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);
});
});