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Testing a button's state with a withRouter-wrapped component

I have a component that is currently wrapped with withRouter (e.g. I use export default withRouter(myComponent)) since I need am using history.push for one of my links within the component. I am writing a test in Enzyme that tests whether a button in that component changes its state to true/false when the user clicks it. The test is failing with the error that it cannot read the property of isExpanded of null. This is what I have for my test:
import React from 'react';
import Adapter from 'enzyme-adapter-react-16';
import { mount, configure } from 'enzyme';
import { MemoryRouter } from 'react-router-dom';
import myComponent from './myComponent';
configure({ adapter: new Adapter() });
describe('Successful flows', () => {
test('button changes state when clicked', () => {
const wrapper = mount(<MemoryRouter><myComponent /></MemoryRouter>);
const moreBtn = wrapper.find('.seeMoreButton').at(0);
moreBtn.simulate('click');
expect(wrapper.state().isExpanded).toEqual(true);
});
});
I have found that before I used withRouter and just had const wrapper = mount(<myComponent />); in my test, the test passed. I am fairly new to routing and I feel like there's something I'm missing here so any help would be appreciated.

You are checking the state of the wrong component, the result of mount will be MemoryRouter, not myComponent.
After you mount the component, you'll need to find myComponent and verify its state instead
test('button changes state when clicked', () => {
const wrapper = mount(<MemoryRouter><myComponent /></MemoryRouter>);
const comp = wrapper.find(myComponent);
const moreBtn = comp.find('.seeMoreButton').at(0);
moreBtn.simulate('click');
expect(comp.state().isExpanded).toEqual(true);
});

Mocking out React.Suspense Whilst Leaving the Rest of React Intact

I'm trying to write a Jest unit test for a component that uses React.Suspense.
Simplified versions of my component modules under test:
MyComponent.js
import React from 'react';
export default () => <h1>Tadaa!!!</h1>;
MySuspendedComponent.js
import React, { Suspense } from 'react';
import MyComponent from './MyComponent';
export default () => (
<Suspense fallback={<div>Loading…</div>}>
<MyComponent />
</Suspense>
);
Naïvely, in my first attempt, I wrote a unit test that uses Enzyme to mount the suspended component:
MySuspendedComponent.test.js
import React from 'react';
import { mount } from 'enzyme';
import MySuspendedComponent from './MySuspendedComponent';
test('the suspended component renders correctly', () => {
const wrapper = mount(<MySuspendedComponent />);
expect(wrapper.html()).toMatchSnapshot();
});
This causes the test to crash with the error message:
Error: Enzyme Internal Error: unknown node with tag 13
Searching for the error message on the web, I found that this is most likely caused by Enzyme not being ready to render Suspense (yet).
If I use shallow instead of mount, the error message changes to:
Invariant Violation: ReactDOMServer does not yet support Suspense
My next attempt was to mock out Suspense with a dummy pass-through component, like this:
MySuspendedComponent.test.js
import React from 'react';
import { mount } from 'enzyme';
import MySuspendedComponent from './MySuspendedComponent';
jest.mock('react', () => {
const react = require.requireActual('react');
return () => ({
...react,
Suspense({ children }) {
return children;
}
});
});
test('the suspended component renders correctly', () => {
const wrapper = mount(<MySuspendedComponent />);
expect(wrapper.html()).toMatchSnapshot();
});
The idea is to have a mock implementation of the React module that contains all the actual code from the React library, with only Suspense being replaced by a mock function.
I've used this pattern with requireActual, as described in the Jest documentation, successfully in other unit tests when mocking other modules than React, but with React, it does not work.
The error I get now is:
TypeError: (($_$w(...) , react) || ($$w(...) , _load_react(...))).default.createElement is not a function
…which, I assume, is caused by the original implementation of React not being available after my mocking trick.
How can I mock out Suspense while leaving the rest of the React library intact?
Or is there another, better way to test suspended components?

The solution is not to use object spreading to export the original React module, but simply overwriting the Suspense property, like this:
MySuspendedComponent.test.js
import React from 'react';
import { mount } from 'enzyme';
import MySuspendedComponent from './MySuspendedComponent';
jest.mock('react', () => {
const React = jest.requireActual('react');
React.Suspense = ({ children }) => children;
return React;
});
test('the suspended component renders correctly', () => {
const wrapper = mount(<MySuspendedComponent />);
expect(wrapper.html()).toMatchSnapshot();
});
This creates the following snapshot, as expected:
MySuspendedComponent.test.js.snap
exports[`the suspended component renders correctly 1`] = `"<h1>Tadaa!!!</h1>"`;

I needed to test my lazy component using Enzyme. Following approach worked for me to test on component loading completion:
const myComponent = React.lazy(() =>
import('#material-ui/icons')
.then(module => ({
default: module.KeyboardArrowRight
})
)
);
Test Code ->
//mock actual component inside suspense
jest.mock("#material-ui/icons", () => {
return {
KeyboardArrowRight: () => "KeyboardArrowRight",
}
});
const lazyComponent = mount(<Suspense fallback={<div>Loading...</div>}>
{<myComponent>}
</Suspense>);
const componentToTestLoaded = await componentToTest.type._result; // to get actual component in suspense
expect(componentToTestLoaded.text())`.toEqual("KeyboardArrowRight");
This is hacky but working well for Enzyme library.

Testing - React stateless components, spying on component methods using sinon

Problem:
I am trying to test the click function of a React stateless component in ES6. However, when using sinon to spy on the handleClick function I get the response...
TypeError: Cannot read property 'goToFullCart' of undefined
I have tried a few other methods. Some of them seem to work when the component is a Class component but all methods seem to fail when using a stateless functional component as follows...
The code:
import React from 'react'
import PropTypes from 'prop-types'
import SVG from '../../../../static/svg/Svg';
import Svgs from '../../../../static/svg/SvgTemplates';
const TestComponent = ({order, router}) => {
const handleClick = (event) => {
event.stopPropagation()
router.push(`/order/${order.orderId}/cart`);
}
return (
<button className="preview-bar" onClick={handleClick}>
<p>Button Content</p>
</button>
)
}
TestComponent.propTypes = {
order: PropTypes.object.isRequired,
router: PropTypes.object.isRequired,
}
export default TestComponent
export { TestComponent }
import React from 'react';
import { shallow, mount } from 'enzyme';
import { expect } from 'chai';
import sinon from 'sinon';
import TestComponent from "./TestComponent"
let wrapper, props;
describe('<TestComponent /> component unit tests', () => {
describe('when the minimized cart is clicked', () => {
beforeEach(function() {
props = {
}
wrapper = shallow((<TestComponent {...props} />))
});
it('should have a goToFullCart method', () => {
const spy = sinon.spy(TestComponent.prototype, 'handleClick');
expect(spy).to.equal(true)
});
});
});
I am at a loss as to how to spy on the handleClick method to check when the button is clicked.
Thanks for the help and discussion. Feel free to ask for any clarification if anything is not clear.
Cheers

A stateless component is basically a function. Good practice not to create another function inside this because it will create a closure, if you wanted to create methods inside component create stateful component rather
Instead of testing handleClick, you can test route is changed or not
import React from 'react';
import {shallow} from 'enzyme';
test('should call handleClick method when button got clicked', () => {
window.location.assign = mock;
wrapper .find('button').simulate('click');
expect(window.location.assign).toHaveBeenCalled(1);
});
Hope this help you!

Unidirectional Data Flow in React with MobX

I'm trying to setup a project architecture using MobX and React and was wondering if doing this following would be considered "not bad". I don't want this question to end up being another "this is a matter of personal preference and so this question doesn't belong here... We can all agree that some things really are bad.
So I'm thinking of only having a single Store.js file that looks something like this:
import { observable, action, useStrict } from 'mobx';
useStrict(true);
export const state = observable({
title: ''
});
export const actions = {
setTitle: action((title) => {
state.title = title;
})
};
Note: that all application state will be in state, there will only be a single store.
I then use state in my root component a.k.a App.js like so:
import React, { Component } from 'react';
import { observer } from 'mobx-react';
import { state } from './Store';
import DisplayTitle from './components/DisplayTitle/DisplayTitle';
import SetTitle from './components/SetTitle/SetTitle';
class App extends Component {
render() {
return (
<div className="App">
<DisplayTitle title={state.title}/>
<SetTitle />
</div>
);
}
}
export default observer(App);
I'll obviously have a whole bunch of components in my app, but none of the components will ever read state directly from Store.js. Only my App.js will import the state and pass it down the component tree.
Another note: I'm not so sure anymore why other components can't read the state directly from Store.js...
This is the case with the DisplayTitle component:
import React, { Component } from 'react';
class DisplayTitle extends Component {
render () {
return (
<h1>{this.props.title}</h1>
);
}
}
export default DisplayTitle;
But, even though no other components can directly import state (except App.js), any component can import actions from Store.js in order to mutate the state.
For example in the SetTitle component:
import React, { Component } from 'react';
import { actions } from './../../Store';
class SetTitle extends Component {
updateTitle (e) {
actions.setTitle(e.currentTarget.value);
}
render () {
return (
<input onChange={this.updateTitle} type='text'/>
);
}
}
export default SetTitle;
Are there any flaws or other obvious reasons why this approach wouldn't be the best route to go? I'd love any and all feedback!

you are missing a few things
at root level:
import { Provider } from 'mobx-react'
...
<Provider state={state}>
<Other stuff />
</Provider>
At component level:
import { inject } from 'mobx-react'
#inject('state')
class Foo ... {
handleClick(){
this.props.state.setTitle('foo')
}
render(){
return <div onClick={() => this.handleClick()}>{this.props.state.title}</div>
}
}
You can stick only the interface actions={actions} in your provider and inject that, ensuring children can call your API methods to mutate state and have it flow from bottom up. Though if you were to mutate it direct, no side effects will happen because all components willReact and update in your render tree - flux is cleaner to reason about.

React - Components using Javascript

I am trying to figure out how to respond to the warning in react to use javascript classes to create components in my MERN app.
The warning says:
Warning: Accessing createClass via the main React package is deprecated, and will be removed in React v16.0. Use a plain JavaScript class instead. If you're not yet ready to migrate, create-react-class v15.* is available on npm as a temporary, drop-in replacement. For more info see[ \[this link\][1]
The link in that message says:
// After (15.5)
var React = require('react');
var createReactClass = require('create-react-class');
var Component = createReactClass({
mixins: [MixinA],
render() {
return <Child />;
}
});
I am using react v 15.5.4
In my app, I have tried to change my components as follows:
import React from 'react';
import ReactDOM from 'react-dom';
import { Button } from 'react-bootstrap';
var createReactClass = require('create-react-class');
var GreeterForm = createReactClass({
onFormSubmit: function(e) {
e.preventDefault();
However, the warning persists. Can anyone see what I have done wrong? How do I implement the new approach to defining components?

You should use ES6 class for make a React component.
import React from 'react';
class App extends from React.Component{
constructor(props){
super(props);
this.sample = this.sample.bind(this);
// initialize your methods, states here
}
// if you want life cycle methods and methods define here
componentWillMount(nextProps, nextState){
console.log('componentWillMount');
}
sample(){
console.log('sample');
}
render(){
return <div onClick={this.sample}>Hello World!</div>
}
}

This is what I would do to create a class in React:
import React, { Component } from 'react';
class GreeterForm extends Component {
onFormSubmit = (e) => {
e.preventDefault();
//do stuff
}
render() {
return (<Child onFormSubmit={this.onFormSubmit} />)
}
}