jest.config.ts

import { existsSync, mkdirSync, readFileSync } from 'fs';
import { defaults } from 'jest-config';
import * as jsonc from 'jsonc-parser';
import { join } from 'path';
import type { JestConfigWithTsJest } from 'ts-jest';

const tsconfigBase: typeof import('./tsconfig.json') = jsonc.parse(
  readFileSync(join(__dirname, 'tsconfig.json'), 'utf-8')
);
const tsconfigJest: typeof import('./tsconfig.build.json') = jsonc.parse(
  readFileSync(join(__dirname, 'tsconfig.build.json'), 'utf-8')
);
const tsconfig = Object.assign(tsconfigBase.compilerOptions, tsconfigJest.compilerOptions);

/**
 * @see {@link https://jestjs.io/docs/configuration}
 * * how to run single test {@link https://stackoverflow.com/questions/28725955/how-do-i-test-a-single-file-using-jest}
 */
const config: JestConfigWithTsJest = {
  preset: 'ts-jest',
  testEnvironment: 'node',
  moduleFileExtensions: [...defaults.moduleFileExtensions, 'mts'],
  verbose: false,
  cache: true,
  cacheDirectory: join(__dirname, 'tmp/jest'),
  collectCoverageFrom: ['src/*.{js,ts}', '!**/node_modules/**', '!**/vendor/**', '!**/test/**', '!**/*.test.{js,ts}'],
  roots: [`<rootDir>/test`],
  coveragePathIgnorePatterns: ['/node_modules/', '/dist/', '/tmp/', '/test/'],

  testMatch: [`**/__tests__/**/*.+(ts|tsx|js)`, `**/?(*.)+(spec|test).+(ts|tsx|js)`, `**/test/*.test.ts`],

  transform: {
    '^.+\\.(ts|tsx)$': [
      'ts-jest',
      // required due to custom location of tsconfig.json configuration file
      // https://kulshekhar.github.io/ts-jest/docs/getting-started/options/tsconfig
      { tsconfig }
    ]
  },

  detectLeaks: true,
  // Automatically clear mock calls, instances, contexts and results before every test
  clearMocks: true,

  // Indicates whether the coverage information should be collected while executing the test
  collectCoverage: true,

  // An array of glob patterns indicating a set of files for which coverage information should be collected
  // collectCoverageFrom: undefined,

  // The directory where Jest should output its coverage files
  coverageDirectory: 'coverage',

  // An array of regexp pattern strings used to skip coverage collection
  // coveragePathIgnorePatterns: [
  //   "\\\\node_modules\\\\"
  // ],

  // Indicates which provider should be used to instrument code for coverage
  coverageProvider: 'v8'

  // A list of reporter names that Jest uses when writing coverage reports
  // coverageReporters: [
  //   "json",
  //   "text",
  //   "lcov",
  //   "clover"
  // ],
};

if (!existsSync(<string>config.cacheDirectory)) mkdirSync(<string>config.cacheDirectory, { recursive: true });

export default config;