Testing components that depend on Context using React Testing Library or Jest

user_10459336 0
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All of my components get data and methods from the Context. I want to test -at least- "component renders" case but of course, when I try to render component in a test case, it cannot find methods/functions and data that come from the Context. I couldn't find a way to pass Context values to a test case using React Testing Library or Jest (I need to use these libraries, no enzyme)

Let's say I want to test a simple Filter component.

Context (primitive usage I guess)

import { useState, useEffect, createContext } from "react";

const Context = createContext();

const ContextProvider = ({ children }) => {
  const [books, setBooks] = useState([]);
  // other data and method code..

  const handleFilter = (value) => {
    const filteredBooks = [...books];
    if (books.length > 0) {
      switch (value) {
        case "alphabetical":
          filteredBooks.sort((a, b) => a.title - b.title);
          setBooks(filteredBooks);
          break;
        case "publishdate":
          filteredBooks.sort(
            (a, b) => b.first_publish_year - a.first_publish_year
          );
          setBooks(filteredBooks);
          break;
        default:
          setBooks(filteredBooks);
      }
    }
  };

  return (
    <Context.Provider value={{ handleFilter }}>
      {children}
    </Context.Provider>
  );
};

export { ContextProvider, Context };

Filter

import { useContext } from "react";
import { Context } from "../context/Context";

function Filter() {
  const { handleFilter } = useContext(Context);

  return (
    <div className="filter" data-testid="filter-test">
      <div className="filter-content">
        <select
          defaultValue="none"
          className="filter-btn"
          onChange={(e) => handleFilter(e.target.value)}
        >
          <option value="none" defaultValue disabled>
            Filter Results
          </option>
          <option value="alphabetical">Alphabetically</option>
          <option value="publishdate">Publish Date (newest)</option>
        </select>
      </div>
    </div>
  );
}

export default Filter;

Filter.test.js

import { render, screen, cleanup } from '@testing-library/react';
import Filter from './Filter';

test('renders Filter component without crashing', () => {
  // I need to pass handleFilter function using Context somehow
  render(<Filter />);
  const filterComponent = screen.getByTestId('filter-test');
  expect(filterComponent).toBeInTheDocument();
});

If you want to see all code: https://codesandbox.io/s/inspiring-bhaskara-0s98g

react-testing-library reactjs
1 Answers

The simple way of doing this is by passing your context provider as a wrapper of the first argument of render():

import { render, screen, cleanup } from '@testing-library/react';
import Filter from './Filter';

// import your context; it will include the provider
import { Context } from "../context/Context";

test('renders Filter component without crashing', () => {
  const contextValue = { handleFilter: () => {} };
  render(
    <Context.Provider value={contextValue}>
      <Filter />
    </Context.Provider>
  );

  const filterComponent = screen.getByTestId('filter-test');
  expect(filterComponent).toBeInTheDocument();
});

The other way is to provide your context as a wrapper to the render:

import { render, screen, cleanup } from '@testing-library/react';
import Filter from './Filter';

// import your context; it will include the provider
import { Context } from "../context/Context";

test('renders Filter component without crashing', () => {
  const contextValue = { handleFilter: () => {} };
  const wrapper = ({ children }) => (
    <Context.Provider value={contextValue}>
      {children}
    </Context.Provider>
  );

  render(<Filter />, { wrapper });

  const filterComponent = screen.getByTestId('filter-test');
  expect(filterComponent).toBeInTheDocument();
});

Either of the above two ways should work

user_17103590
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