npm i jest ts-jest @types/jest -D

npx jest --init

npm i jest-environment-jsdom eslint-plugin-jest eslint-import-resolver-typescript jest-canvas-mock -D

/*
 * For a detailed explanation regarding each configuration property, visit:
 * https://jestjs.io/docs/configuration
 */

const { pathsToModuleNameMapper } = require('ts-jest');
const { compilerOptions } = require('./tsconfig.json');

module.exports = {
  // A preset that is used as a base for Jest's configuration
  preset: 'ts-jest',
  // The test environment that will be used for testing
  testEnvironment: 'jsdom',
  // The paths to modules that run some code to configure or set up the testing environment before each test
  setupFiles: ['jest-canvas-mock'],
  // 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,
  // The directory where Jest should output its coverage files
  coverageDirectory: 'test/coverage',
  // The root directory that Jest should scan for tests and modules within
  // rootDir: undefined,
  // rootDir: __dirname,
  // An array of file extensions your modules use
  moduleFileExtensions: ['ts', 'js'],
  // A map from regular expressions to module names or to arrays of module names that allow to stub out resources with a single module
  moduleNameMapper: pathsToModuleNameMapper(compilerOptions.paths, {
    prefix: '<rootDir>/',
  }),
  // The glob patterns Jest uses to detect test files
  testMatch: ['<rootDir>/test/__tests__/**/*.test.ts'],
  // A map from regular expressions to paths to transformers
  transform: {
    '^.+\\.ts$': 'ts-jest',
  },
};

module.exports = {
  extends: ['../.eslintrc.js'],
  settings: {
    'import/resolver': {
      typescript: {
        alwaysTryTypes: true, // always try to resolve types under `<root>@types` directory even it doesn't contain any source code, like `@types/unist`

        // Choose from one of the "project" configs below or omit to use <root>/tsconfig.json by default
        // use <root>/path/to/folder/tsconfig.json
        project: 'tsconfig.json',
      },
    },
  },
  plugins: ['jest'],
  overrides: [
    // unit-tests
    {
      files: ['**/__tests__/**'],
      rules: {
        'jest/no-disabled-tests': 'warn',
        'jest/no-focused-tests': 'error',
        'jest/no-identical-title': 'error',
        'jest/prefer-to-have-length': 'warn',
        'jest/valid-expect': 'error',
      },
    },
  ],
};

...

# Unit test / coverage reports
test/coverage