Test component with context and react hook - reactjs

Question

I have a simple Dashboard component that relies on React context to manage auth. It contains a custom hook useAuth to extract the current user as well as the auth related functions: login, logout, etc.
This is the Context file: AuthContext.js:
import React, { createContext, useContext, useState, useEffect } from "react";
import { auth } from "../config/firebase";
const AuthContext = createContext();
export function useAuth() {
return useContext(AuthContext);
}
export function AuthProvider({ children }) {
const [currentUser, setCurrentUser] = useState();
const [loading, setLoading] = useState(true);
function signup(email, password) {
return auth.createUserWithEmailAndPassword(email, password);
}
function login(email, password) {
return auth.signInWithEmailAndPassword(email, password);
}
function logout() {
return auth.signOut();
}
useEffect(() => {
const unsubscribe = auth.onAuthStateChanged((user) => {
setCurrentUser(user);
setLoading(false);
});
return unsubscribe;
}, []);
const value = {
currentUser,
signup,
login,
logout,
};
return (
<AuthContext.Provider value={value}>
{!loading && children}
</AuthContext.Provider>
);
}
This is the Dashboard.js component:
import React, { useState } from "react";
import { useHistory } from "react-router-dom";
import { useAuth } from "../context/AuthContext";
export default function Dashboard() {
const { currentUser, logout } = useAuth();
const [error, setError] = useState("");
const history = useHistory();
const handleLogout = async () => {
setError("");
try {
await logout();
history.push("/login");
} catch (e) {
setError(e.message);
}
};
return (
<div>
{error && <p>{error}</p>}
<h1>This is the Dashboard</h1>
<h5>Email: {currentUser.email}</h5>
<button onClick={handleLogout} type="button">
Logout
</button>
</div>
);
}
As recommened by React Testing Library I have created a test-utils.js file:
import React, { createContext } from "react";
import { render } from "#testing-library/react";
import { BrowserRouter as Router } from "react-router-dom";
const AuthContext = createContext();
const currentUser = {
email: "abc#abc.com",
};
const signup = jest.fn();
const login = jest.fn();
const logout = jest.fn();
const AllTheProviders = ({ children }) => {
return (
<Router>
<AuthContext.Provider value={{ currentUser, signup, login, logout }}>
{children}
</AuthContext.Provider>
</Router>
);
};
const customRender = (ui, options) => {
render(ui, { wrapper: AllTheProviders, ...options });
};
export * from "#testing-library/react";
export { customRender as render };
However, when running Dashboard.test.js I get error
TypeError: Cannot destructure property 'currentUser' of '((cov_5mwatn2cf(...).s[0]++) , (0 , _AuthContext.useAuth)(...))' as it is undefined.
4 |
5 | export default function Dashboard() {
> 6 | const { currentUser, logout } = useAuth();
| ^
7 | const [error, setError] = useState("");
8 | const history = useHistory();
import React from "react";
import Dashboard from "./Dashboard";
import { act, render, screen } from "../config/test-utils-dva";
beforeEach(async () => {
await act(async () => {
render(<Dashboard />);
});
});
test("displays dashboard", () => {
expect(screen.getByText(/dashboard/i)).toBeInTheDocument();
});
I think it is because Dashboard component is trying to use useAuth from AuthContext.js, how can I force the rendered Dashboard component to use the mocked data that I am sending in the test-utils.jsfile?

Answer 1

Instead of creating a new context, use the AuthContext from context/AuthContext for <AuthContext.Provider>, as that's the context that the hook uses.
So, in AuthContext.js, export the context instance:
export const AuthContext = createContext();
Then, in your test-util.js file, instead of again calling createContext (which will create a completely separate context instance - the contexts are not the same even if they are stored in a variable with the same name!), just import the previously exported instance:
import { AuthContext } from "../context/AuthContext";
const AllTheProviders = ({ children }) => {
return (
<Router>
<AuthContext.Provider value={{ currentUser, signup, login, logout }}>
{children}
</AuthContext.Provider>
</Router>
);
};