Testing React Apps the Right Way

I was having endless trouble with tests in my React app, and it was causing my build pipeline to fail as well.

After a few hours of reading documents and cobbling answers from around the forums I found a great, highly flexible solution. There are several places I needed to configure correctly so I'm listing them out below for anyone else that is trying to get their tests up and running and not having any luck.

Setup your package.json to include these dependencies, and jest configuration:

"devDependencies": {
    "@babel/plugin-transform-runtime": "^7.12.10",
    "@babel/preset-env": "7.12.11",
    "@babel/preset-react": "7.12.10",
    "babel-jest": "26.6.3",
    "babel-plugin-transform-class-properties": "^6.24.1",
    "chai": "^4.2.0",
    "enzyme": "^3.11.0",
    "enzyme-adapter-react-16": "^1.15.5",
    "enzyme-to-json": "^3.6.1",
    "jest": "26.6.3",
    "node-sass": "4.14.1",
    "react-test-renderer": "17.0.1",
    "redux-mock-store": "^1.5.4"
  },

...other stuff---

"jest": {
    "moduleNameMapper": {
      "\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$": "<rootDir>/__mocks__/fileMock.js",
      "\\.(css|less|scss)$": "<rootDir>/__mocks__/styleMock.js"
    }
  }

Basic test:

// <rootdir>/__tests__/app.test.js
import React from "react";
import { assert } from "chai";
import { shallow, configure } from "enzyme";
import Adapter from "enzyme-adapter-react-16";
import configureMockStore from "redux-mock-store";
import { Provider } from "react-redux";

import App from "../src/App"; // Component to Test

configure({ adapter: new Adapter() });

const mockStore = configureMockStore();
const store = mockStore({});

describe("Test Component", () => {
  it("render correctly App component", () => {
    const AppComponent = shallow(
      <Provider store={store}>
        <App />
      </Provider>
    ).exists();
    assert(AppComponent === true);
  });
});

Add these styleMock and filemock modules to prevent errors on jsx components importing css/scss and/or files:

// <rootdir>/__mocks__/styleMock.js
module.exports = {};

// <rootdir>/__mocks__/fileMock.js
module.exports = "test-file-stub";

// <rootdir>/babel.config.js
module.exports = {
  presets: ["@babel/preset-env", "@babel/preset-react"],
  plugins: [
    "@babel/plugin-proposal-class-properties",
    "@babel/plugin-transform-runtime",
  ],
};