React Testing Library / Redux - How to mock cookies?

Question

Issue

I'm able to mock the cookie in Jest, but it won't change the state of my components once the cookie is mocked.

For example, when a user visits my app, I want to check if a cookie of ACCESS_TOKEN exists, if it exists, render a saying "Hi, Username".

When testing, I'm able to create the cookie and get the values with console.log(), but my component won't render the because the test does not think redux-store has the cookie.

Here's what my redux-store looks like (Redux store is not the problem, all my tests that does not rely on cookies and soley relies on store are working):

Root.tsx

export const store = createStore(
    reducers,
    { authStatus: { authenticated: Cookies.get("ACCESS_TOKEN") } },
    //if our inital state (authStauts) has a cookie, keep them logged in
    composeWithDevTools(applyMiddleware(reduxThunk))
);

const provider = ({ initialState = {}, children }) => {
    return <Provider store={store}>{children}</Provider>;
};

export default provider

App.tsx

import Root from "./Root"; //root is provider variable in Root.tsx
ReactDOM.render(
    <React.StrictMode>
        <Root>
            <App />
        </Root>
    </React.StrictMode>,
    document.getElementById("root")
);

Welcome.tsx

const Welcome =(props) => {

    return(
      <div>
        {props.authStatus && <h3> Hello USERNAME</h3>}
     </div>
    }
   }

const mapStateToProps = (state) => {
    return {
        authStatus: state.authStatus.authenticated,
    };
};

export default connect(mapStateToProps, {})(Welcome);

Here's my test:

import Cookies from "js-cookie"

beforeEach(async () => {
   //Before the component renders, create a cookie of ACCESS_TOKEN.

    //Method 1 (Works, console.log() below would show the value, but component won't render):
    //jest.mock("js-cookie", () => ({ get: () => "fr" }));

    //Method 2 (Works, console.log() below would show the value, but component won't render):
    //Cookies.get = jest.fn().mockImplementation(() => "ACCESS_TOKEN");

    //Method 3 (Works, console.log() below would show the value, but component won't render)):
    // Object.defineProperty(window.document, "cookie", {
    //     writable: true,
    //     value: "myCookie=omnomnom",
    // });


    app = render(
        <Root>
            <MemoryRouter initialEntries={["/"]} initialIndex={0}>
                <Routes />
            </MemoryRouter>
        </Root>
    );
    console.log("Cookie Val", Cookies.get());
    app.debug(); //I want to see that the <h3> is rendered, but it's not being rendered.
});

Why is this occurring?

Resources used:

How to mock Cookie.get('language') in JEST

Use Jest to test secure cookie value

Answer 1

I'm not exactly sure how did you combine things together but I'm gonna drop you a full example that you can follow and fix your code as bellow, please check inline comments:

// Provider.jsx
import React from 'react';
import { createStore } from 'redux';
import { Provider } from 'react-redux';
import Cookies from "js-cookie";

// the reducer I assume as same as you created
const authReducer = (state = {}, action) => {
  return {
    ...state,
    ...action.payload,
  }
}

const store = createStore(
    authReducer,
    { authStatus: { authenticated: Cookies.get("ACCESS_TOKEN") } }
);

export default ({ initialState = {}, children }) => {
    return <Provider store={store}>{children}</Provider>;
};

// Routes.jsx
// should be the same as you did
import React from 'react';
import { Switch, Route } from 'react-router-dom';
import Welcome from "./Welcome";

export default (props) => {
    return (
        <Switch>
          <Route exact path="/" component={Welcome} />
        </Switch>
    )
}

Finally the test file:

// index.test.js
import React from 'react';
import Cookies from "js-cookie"
import "@testing-library/jest-dom"
import { screen, render } from '@testing-library/react';
import { MemoryRouter } from 'react-router-dom';
import Routes from "./Routes";
import Provider from "./Provider";

// Mock your cookie as same you did 
// but should be the same level with `import` things
jest.mock("js-cookie", () => ({ get: () => "fr" }), {
   // this just for being lazy to install the module :)
   virtual: true
});

it('should pass', () => {
    render(
        <Provider>
            <MemoryRouter initialEntries={["/"]} initialIndex={0}>
                <Routes />
            </MemoryRouter>
        </Provider>
    );

    expect(screen.queryByText('Hello USERNAME')).toBeInTheDocument()
})

PS: The link I created the test for you: https://repl.it/@tmhao2005/js-cra (ref at src/Redux to see full example)