jest.config.js

// Taken from:
// https://nextjs.org/docs/pages/building-your-application/optimizing/testing#setting-up-jest-with-babel

const esModules = [
  "mdast[^/]*",
  "micromark[^/]*",
  "unist[^/]*",
  "remark[^/]*",
  "react[^/]*",
  "unified",
  "bail",
  "trough",
  "vfile",
  "vfile-message",
  "is-plain-obj",
  "decode-named-character-reference",
  "trim-lines",
  "property-information",
  "hast-util-whitespace",
  "space-separated-tokens",
  "comma-separated-tokens",
];

module.exports = {
  collectCoverage: true,
  // on node 14.x coverage provider v8 offers good speed and more or less good report
  coverageProvider: "v8",
  collectCoverageFrom: [
    "**/*.{js,jsx,ts,tsx}",
    "!**/*.d.ts",
    "!**/node_modules/**",
    "!<rootDir>/out/**",
    "!<rootDir>/.next/**",
    "!<rootDir>/*.config.js",
    "!<rootDir>/coverage/**",
  ],
  moduleNameMapper: {
    // Handle CSS imports (with CSS modules)
    // https://jestjs.io/docs/webpack#mocking-css-modules
    "^.+\\.module\\.(css|sass|scss)$": "identity-obj-proxy",

    // Handle CSS imports (without CSS modules)
    "^.+\\.(css|sass|scss)$": "<rootDir>/__mocks__/styleMock.js",

    // Handle image imports
    // https://jestjs.io/docs/webpack#handling-static-assets
    "^.+\\.(png|jpg|jpeg|gif|webp|avif|ico|bmp|svg)$/i": `<rootDir>/__mocks__/fileMock.js`,

    // Handle alias imports
    "^@/(.*)$": "<rootDir>/$1",
  },
  // Add more setup options before each test is run
  // setupFilesAfterEnv: ['<rootDir>/jest.setup.js'],
  testPathIgnorePatterns: ["<rootDir>/../../node_modules/", "<rootDir>/.next/"],
  testEnvironment: "jsdom",
  transform: {
    // Use babel-jest to transpile tests with the next/babel preset
    // https://jestjs.io/docs/configuration#transform-objectstring-pathtotransformer--pathtotransformer-object
    "^.+\\.(js|jsx|ts|tsx)$": ["babel-jest", { presets: ["next/babel"] }],
  },
  transformIgnorePatterns: [
    `/node_modules/(?!(${esModules.join("|")})/)`,
    "^.+\\.module\\.(css|sass|scss)$",
  ],
  setupFiles: ["jest-canvas-mock", "<rootDir>/setupTests.js"],
};