Next.js 13.4 & Jest & Cypress Setup Guide

Getting Started with Next 13.4

How I set up a project

This is a step-by-step guide to make a Next.js project with:

1. TypeScript for type safety
2. Tailwind CSS for styling
3. Jest for testing components etc.
4. Cypress for end to end testing etc.
5. ESLint for linting
6. Prettier for formatting
7. Husky & Lint-Staged for pre-commit testing and linting

If you like this, checkout my other projects on GitHub or via my Portfolio

You can also read this guide on my blog

TLDR: This setup is available as a template in my GitHub Account if you want the quickest path to the end result or want to see the setup in context- GLD-NextTemplate

Installation and Repo setup

1. npx create-next-app@latest
2. code my-app
3. git init
4. gh repo create
5. git add .
6. git commit . -m "Initial Commit"
7. git push -u origin main

Setup Testing

Jest

1. Install Jest, ts-jest, jsdom, testing libraries & eslint plugins: npm i -D jest ts-jest jest-environment-jsdom @testing-library/jest-dom @testing-library/react eslint-plugin-jest-dom eslint-plugin-testing-library
2. Add jest.config.mjs

import nextJest from "next/jest.js";

const createJestConfig = nextJest({
  // Provide the path to your Next.js app to load next.config.js and .env files in your test environment
  dir: "./",
});

// Add any custom config to be passed to Jest
/** @type {import('jest').Config} */
const config = {
  // Add more setup options before each test is run
  setupFilesAfterEnv: ["<rootDir>/jest.setup.js"],

  testEnvironment: "jest-environment-jsdom",
};

// createJestConfig is exported this way to ensure that next/jest can load the Next.js config which is async
export default createJestConfig(config);

1. Add jest.setup.js:

import '@testing-library/jest-dom/extend-expect'
import React from 'react'

function MockImage(props) {
    return React.createElement('img', props)
}
jest.mock('next/image', () => MockImage)

1. Add scripts to package.json:

  "scripts": {
    "test": "clear && jest",
    "test:noClear": "jest",
    "test:watch": "clear && jest --watchAll",
  }

1. Add first test in \_\_tests\_\_/home.test.tsx:

import React from 'react';
import { render } from '@testing-library/react';
import Home from '@/app/page';

describe('Home component', () => {
  it('renders correctly', () => {
    render(<Home />);

    const heroHeading = screen.getByTestId('hero-heading');
    expect(heroHeading).toBeInTheDocument();

    const madeByText = screen.getByText(/Made by GLD5000/i);
    expect(madeByText).toBeInTheDocument();

  });
});

Cypress

1. Install latest Cypress: npm i -D cypress@latest (currently "cypress": "^12.17.3" at time of writing)

2. Start a dev server in a terminal: npm run dev

3. Open Cypress from a second terminal: npx cypress open

4. Once open, click 'E2E Testing' button to configure and then click 'continue' (if you get an error relating to 'bundle' you may need to switch tsconfig.json "moduleResolution": "bundler", to "moduleResolution": "node",), when prompted for a browser choose e.g. Chrome and click to add scaffolded examples if you like.

5. Setup new config files within the 'cypress' folder:

cypress/eslintrc.json with disabled rules to accommodate cypress example specs:

{
    "plugins": ["cypress"],
    "extends": ["plugin:cypress/recommended"],
    "rules": {
        "testing-library/await-async-utils": "off",
        "no-unused-expressions": "off",
        "@typescript-eslint/ban-ts-comment": "off",
        "cypress/unsafe-to-chain-command": "off",
        "@typescript-eslint/no-unused-vars": "off",
        "@typescript-eslint/no-empty-function": "off",
        "func-names": "off",
        "@typescript-eslint/no-var-requires": "off",
        "global-require": "off",
        "testing-library/no-debugging-utils": "off",
        "no-param-reassign": "off"
    },
    "overrides": [
        {
            "files": ["viewport.cy.js", "waiting.cy.js"],
            "rules": {
                "cypress/no-unnecessary-waiting": "off"
            }
        }
    ]
}

cypress/tsconfig.json:

{
    "compilerOptions": {
        "target": "es5",
        "lib": ["es5", "dom", "dom.iterable", "esnext"],
        "allowJs": true,
        "skipLibCheck": true,
        "strict": true,
        "forceConsistentCasingInFileNames": true,
        "noEmit": true,
        "esModuleInterop": true,
        "module": "esnext",
        "moduleResolution": "node",
        "resolveJsonModule": true,
        "isolatedModules": true,
        "jsx": "preserve",
        "incremental": true,
        "plugins": [
            {
                "name": "next"
            }
        ],
        "paths": {
            "@/*": ["./src/*"]
        }
    },
    "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", ".next/types/**/*.ts"],
    "exclude": ["node_modules"]
}

1. Update exclude and include in root tsconfig.json:

    "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", ".next/types/**/*.ts","cypress/tsconfig.json"],
    "exclude": ["node_modules", "./cypress.config.ts","cypress"]

1. Put an eslint disable comment in the cypress.config.ts:

/* eslint-disable */
import { defineConfig } from "cypress";

export default defineConfig({
  e2e: {
    setupNodeEvents(on, config) {
      // implement node event listeners here
    },
  },
});

1. Add script to package.json:

  "scripts": {
    ...
   "cypress": "npx cypress open"
  }

1. Add first test:

• Add data-testid attribute to H1 on app/page.tsx:

    <h1 data-testid="hero-heading" className="w-fit mx-auto text-5xl font-bold text-center">
                Minimal Starter Template for
            </h1>

• Add test in cypress/e2e/home.cy.ts:

describe("template spec", () => {
  it("H1 contains correct text", () => {
    cy.visit("http://localhost:3000/");
    cy.get("[data-testid='hero-heading']").contains("Minimal Starter Template for");
  });
});

Setup Linting

1. Install prettier: npm i -D prettier eslint-plugin-prettier eslint-config-prettier
2. Make prettier config e.g.: touch .prettierrc.js
3. Configure prettier e.g.:

export default {
    trailingComma: "es5",
    tabWidth: 4,
    semi: false,
    singleQuote: true,
};

1. Setup eslint: npm init @eslint/config
2. Install Eslint AirBnb: npm i -D eslint-config-airbnb
3. Get peer dependency list for AirBnb config: list peer dependencies npm info "eslint-config-airbnb@latest" e.g.:

   eslint: '^7.32.0 || ^8.2.0',
  'eslint-plugin-import': '^2.25.3',
  'eslint-plugin-jsx-a11y': '^6.5.1',
  'eslint-plugin-react': '^7.28.0',
  'eslint-plugin-react-hooks': '^4.3.0'

1. Paste into package.json devDependencies and watch for conflicts (duplicates) you will not need eslint if it is already installed with Next.js.
2. Run npm install to install the extra dependencies: npm i
3. Install Eslint typescript: npm i -D @typescript-eslint/parser @typescript-eslint/eslint-plugin eslint-config-airbnb-typescript
4. Install testing plugins: npm i -D eslint-plugin-jest-dom eslint-plugin-testing-library
5. Update eslint config e.g.:

module.exports = {
    extends: [
        'next/core-web-vitals',
        'plugin:testing-library/react',
        'plugin:jest-dom/recommended',
        'airbnb',
        'prettier',
        'eslint:recommended',
        'plugin:react/recommended',
        'plugin:react/jsx-runtime',
        'plugin:@typescript-eslint/recommended',
    ],
    plugins: ['prettier', 'react'],
    ignorePatterns: ['*.ttf', '*.css'],
    rules: {
        '@next/next/no-img-element': 'off',
        'import/no-extraneous-dependencies': 'off',
        'react/require-default-props': 'off',
        'react/jsx-props-no-spreading': 'off',
        'react/jsx-no-useless-fragment': 'off',
        'no-undef': 'off',
        'import/extensions': 'off',
        'react/jsx-uses-react': 'error',
        'react/jsx-uses-vars': 'error',
        'no-console': 'off',
        'react/jsx-no-bind': 'off',
        'react/prop-types': 'off',
        'no-use-before-define': ['error', { functions: false }],
        'react/jsx-filename-extension': 'off',
        'prettier/prettier': ['error'],
        'jsx-a11y/label-has-associated-control': [
            2,
            {
                controlComponents: [
                    'InputSelect',
                    'SectionTitle',
                    'InputTitle',
                    'InputText',
                ],
                depth: 3,
            },
        ],
    },
}

Setup Linting Pre Hooks

1. npm i -D husky
2. npm pkg set scripts.prepare="husky install"
3. npm i or npm run prepare
4. npm install -D lint-staged
5. Add hook: npx husky add .husky/pre-commit "npx lint-staged"
6. Make lint-staged configuration file:touch lint-staged.config.js
7. Add lint-staged configuration e.g.:

module.exports = {
    // this will check Typescript files
    '**/*.(ts|tsx)': () => 'yarn tsc --noEmit',

    // This will format and lint TS & JS Files
    '**/*.(ts|tsx|js)': (filenames) => [
        `yarn prettier --write ${filenames.join(' ')}`,
        `yarn eslint --fix --max-warnings=0 ${filenames.join(' ')}`,
    ],

    // this will Format MarkDown and JSON
    '**/*.(md|json)': (filenames) =>
        `yarn prettier --write ${filenames.join(' ')}`,
}

1. Add optional testing hook e.g.: npx husky add .husky/pre-commit "npm run test:noClear" so your pre-commit file could look something like this:

#!/usr/bin/env sh
. "$(dirname -- "$0")/_/husky.sh"

npm run test:noClear
npx lint-staged

Setup Additional Scripts

Package.json:

    "lint": "clear && next lint",
    "test": "clear && jest",
    "test:noClear": "jest",
    "test:watch": "clear && jest --watchAll",
    "test:v": "clear && jest --verbose",
    "format": "clear && prettier \"src/**/*.{js,jsx,ts,tsx,css,scss}\" --write",
    "lint:fix": "clear && prettier \"src/**/*.{js,jsx,ts,tsx,css,scss}\" --write && eslint src --ext .js,.jsx,.ts,.tsx --fix",
    "lint:all": "clear && prettier \"src/**/*.{js,jsx,ts,tsx,css,scss}\" --write && eslint src --ext .js,.jsx,.ts,.tsx --fix && tsc --noEmit"

That's It!

Not exactly a short process but this will give a really useful base to build quality code with. Don't forget to like / star if you found this useful! If you like, you can also check out my other projects and blogs.