How to use createScriptTransformer method in Jest

Best JavaScript code snippet using jest

ScriptTransformer.js

Source:ScriptTransformer.js

...768    return this._config.transform.length !== 0 && !isIgnored;769  }770} // TODO: do we need to define the generics twice?771async function createTranspilingRequire(config) {772  const transformer = await createScriptTransformer(config);773  return async function requireAndTranspileModule(774    resolverPath,775    applyInteropRequireDefault = false776  ) {777    const transpiledModule = await transformer.requireAndTranspileModule(778      resolverPath,779      () => {},780      {781        applyInteropRequireDefault,782        instrument: false,783        supportsDynamicImport: false,784        // this might be true, depending on node version.785        supportsExportNamespaceFrom: false,786        supportsStaticESM: false,787        supportsTopLevelAwait: false788      }789    );790    return transpiledModule;791  };792}793const removeFile = path => {794  try {795    fs().unlinkSync(path);796  } catch {}797};798const stripShebang = content => {799  // If the file data starts with a shebang remove it. Leaves the empty line800  // to keep stack trace line numbers correct.801  if (content.startsWith('#!')) {802    return content.replace(/^#!.*/, '');803  } else {804    return content;805  }806};807/**808 * This is like `writeCacheFile` but with an additional sanity checksum. We809 * cannot use the same technique for source maps because we expose source map810 * cache file paths directly to callsites, with the expectation they can read811 * it right away. This is not a great system, because source map cache file812 * could get corrupted, out-of-sync, etc.813 */814function writeCodeCacheFile(cachePath, code) {815  const checksum = (0, _crypto().createHash)('md5').update(code).digest('hex');816  writeCacheFile(cachePath, checksum + '\n' + code);817}818/**819 * Read counterpart of `writeCodeCacheFile`. We verify that the content of the820 * file matches the checksum, in case some kind of corruption happened. This821 * could happen if an older version of `jest-runtime` writes non-atomically to822 * the same cache, for example.823 */824function readCodeCacheFile(cachePath) {825  const content = readCacheFile(cachePath);826  if (content == null) {827    return null;828  }829  const code = content.substring(33);830  const checksum = (0, _crypto().createHash)('md5').update(code).digest('hex');831  if (checksum === content.substring(0, 32)) {832    return code;833  }834  return null;835}836/**837 * Writing to the cache atomically relies on 'rename' being atomic on most838 * file systems. Doing atomic write reduces the risk of corruption by avoiding839 * two processes to write to the same file at the same time. It also reduces840 * the risk of reading a file that's being overwritten at the same time.841 */842const writeCacheFile = (cachePath, fileData) => {843  try {844    (0, _writeFileAtomic().sync)(cachePath, fileData, {845      encoding: 'utf8',846      fsync: false847    });848  } catch (e) {849    if (cacheWriteErrorSafeToIgnore(e, cachePath)) {850      return;851    }852    e.message =853      'jest: failed to cache transform results in: ' +854      cachePath +855      '\nFailure message: ' +856      e.message;857    removeFile(cachePath);858    throw e;859  }860};861/**862 * On Windows, renames are not atomic, leading to EPERM exceptions when two863 * processes attempt to rename to the same target file at the same time.864 * If the target file exists we can be reasonably sure another process has865 * legitimately won a cache write race and ignore the error.866 */867const cacheWriteErrorSafeToIgnore = (e, cachePath) =>868  process.platform === 'win32' &&869  e.code === 'EPERM' &&870  fs().existsSync(cachePath);871const readCacheFile = cachePath => {872  if (!fs().existsSync(cachePath)) {873    return null;874  }875  let fileData;876  try {877    fileData = fs().readFileSync(cachePath, 'utf8');878  } catch (e) {879    e.message =880      'jest: failed to read cache file: ' +881      cachePath +882      '\nFailure message: ' +883      e.message;884    removeFile(cachePath);885    throw e;886  }887  if (fileData == null) {888    // We must have somehow created the file but failed to write to it,889    // let's delete it and retry.890    removeFile(cachePath);891  }892  return fileData;893};894const getScriptCacheKey = (filename, instrument) => {895  const mtime = fs().statSync(filename).mtime;896  return filename + '_' + mtime.getTime() + (instrument ? '_instrumented' : '');897};898const calcIgnorePatternRegExp = config => {899  if (900    !config.transformIgnorePatterns ||901    config.transformIgnorePatterns.length === 0902  ) {903    return undefined;904  }905  return new RegExp(config.transformIgnorePatterns.join('|'));906};907const calcTransformRegExp = config => {908  if (!config.transform.length) {909    return undefined;910  }911  const transformRegexp = [];912  for (let i = 0; i < config.transform.length; i++) {913    transformRegexp.push([914      new RegExp(config.transform[i][0]),915      config.transform[i][1],916      config.transform[i][2]917    ]);918  }919  return transformRegexp;920};921function invariant(condition, message) {922  if (!condition) {923    throw new Error(message);924  }925}926function assertSyncTransformer(transformer, name) {927  invariant(name);928  invariant(929    typeof transformer.process === 'function',930    (0, _runtimeErrorsAndWarnings.makeInvalidSyncTransformerError)(name)931  );932}933async function createScriptTransformer(config, cacheFS = new Map()) {934  const transformer = new ScriptTransformer(config, cacheFS);935  await transformer.loadTransformers();936  return transformer;...

generateEmptyCoverage.js

Source:generateEmptyCoverage.js

1'use strict';2Object.defineProperty(exports, '__esModule', {3  value: true4});5exports.default = generateEmptyCoverage;6function fs() {7  const data = _interopRequireWildcard(require('graceful-fs'));8  fs = function () {9    return data;10  };11  return data;12}13function _istanbulLibCoverage() {14  const data = require('istanbul-lib-coverage');15  _istanbulLibCoverage = function () {16    return data;17  };18  return data;19}20function _istanbulLibInstrument() {21  const data = require('istanbul-lib-instrument');22  _istanbulLibInstrument = function () {23    return data;24  };25  return data;26}27function _transform() {28  const data = require('@jest/transform');29  _transform = function () {30    return data;31  };32  return data;33}34function _getRequireWildcardCache(nodeInterop) {35  if (typeof WeakMap !== 'function') return null;36  var cacheBabelInterop = new WeakMap();37  var cacheNodeInterop = new WeakMap();38  return (_getRequireWildcardCache = function (nodeInterop) {39    return nodeInterop ? cacheNodeInterop : cacheBabelInterop;40  })(nodeInterop);41}42function _interopRequireWildcard(obj, nodeInterop) {43  if (!nodeInterop && obj && obj.__esModule) {44    return obj;45  }46  if (obj === null || (typeof obj !== 'object' && typeof obj !== 'function')) {47    return {default: obj};48  }49  var cache = _getRequireWildcardCache(nodeInterop);50  if (cache && cache.has(obj)) {51    return cache.get(obj);52  }53  var newObj = {};54  var hasPropertyDescriptor =55    Object.defineProperty && Object.getOwnPropertyDescriptor;56  for (var key in obj) {57    if (key !== 'default' && Object.prototype.hasOwnProperty.call(obj, key)) {58      var desc = hasPropertyDescriptor59        ? Object.getOwnPropertyDescriptor(obj, key)60        : null;61      if (desc && (desc.get || desc.set)) {62        Object.defineProperty(newObj, key, desc);63      } else {64        newObj[key] = obj[key];65      }66    }67  }68  newObj.default = obj;69  if (cache) {70    cache.set(obj, newObj);71  }72  return newObj;73}74/**75 * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.76 *77 * This source code is licensed under the MIT license found in the78 * LICENSE file in the root directory of this source tree.79 */80async function generateEmptyCoverage(81  source,82  filename,83  globalConfig,84  config,85  changedFiles,86  sourcesRelatedToTestsInChangedFiles87) {88  const coverageOptions = {89    changedFiles,90    collectCoverage: globalConfig.collectCoverage,91    collectCoverageFrom: globalConfig.collectCoverageFrom,92    collectCoverageOnlyFrom: globalConfig.collectCoverageOnlyFrom,93    coverageProvider: globalConfig.coverageProvider,94    sourcesRelatedToTestsInChangedFiles95  };96  let coverageWorkerResult = null;97  if ((0, _transform().shouldInstrument)(filename, coverageOptions, config)) {98    if (coverageOptions.coverageProvider === 'v8') {99      const stat = fs().statSync(filename);100      return {101        kind: 'V8Coverage',102        result: {103          functions: [104            {105              functionName: '(empty-report)',106              isBlockCoverage: true,107              ranges: [108                {109                  count: 0,110                  endOffset: stat.size,111                  startOffset: 0112                }113              ]114            }115          ],116          scriptId: '0',117          url: filename118        }119      };120    }121    const scriptTransformer = await (0, _transform().createScriptTransformer)(122      config123    ); // Transform file with instrumentation to make sure initial coverage data is well mapped to original code.124    const {code} = await scriptTransformer.transformSourceAsync(125      filename,126      source,127      {128        instrument: true,129        supportsDynamicImport: true,130        supportsExportNamespaceFrom: true,131        supportsStaticESM: true,132        supportsTopLevelAwait: true133      }134    ); // TODO: consider passing AST135    const extracted = (0, _istanbulLibInstrument().readInitialCoverage)(code); // Check extracted initial coverage is not null, this can happen when using /* istanbul ignore file */136    if (extracted) {137      coverageWorkerResult = {138        coverage: (0, _istanbulLibCoverage().createFileCoverage)(139          extracted.coverageData140        ),141        kind: 'BabelCoverage'142      };143    }144  }145  return coverageWorkerResult;...

createRuntime.js

Source:createRuntime.js

...79    maxWorkers: 1,80    resetCache: false,81  }).build();82  const cacheFS = new Map();83  const scriptTransformer = await createScriptTransformer(config, cacheFS);84  const runtime = new Runtime(85    config,86    environment,87    Runtime.createResolver(config, hasteMap.moduleMap),88    scriptTransformer,89    cacheFS,90    {91      changedFiles: undefined,92      collectCoverage: false,93      collectCoverageFrom: [],94      collectCoverageOnlyFrom: undefined,95      coverageProvider: 'v8',96      sourcesRelatedToTestsInChangedFiles: undefined,97    },...

runGlobalHook.js

Source:runGlobalHook.js

1'use strict';2Object.defineProperty(exports, '__esModule', {3  value: true4});5exports.default = runGlobalHook;6function util() {7  const data = _interopRequireWildcard(require('util'));8  util = function () {9    return data;10  };11  return data;12}13function _transform() {14  const data = require('@jest/transform');15  _transform = function () {16    return data;17  };18  return data;19}20function _prettyFormat() {21  const data = _interopRequireDefault(require('pretty-format'));22  _prettyFormat = function () {23    return data;24  };25  return data;26}27function _interopRequireDefault(obj) {28  return obj && obj.__esModule ? obj : {default: obj};29}30function _getRequireWildcardCache(nodeInterop) {31  if (typeof WeakMap !== 'function') return null;32  var cacheBabelInterop = new WeakMap();33  var cacheNodeInterop = new WeakMap();34  return (_getRequireWildcardCache = function (nodeInterop) {35    return nodeInterop ? cacheNodeInterop : cacheBabelInterop;36  })(nodeInterop);37}38function _interopRequireWildcard(obj, nodeInterop) {39  if (!nodeInterop && obj && obj.__esModule) {40    return obj;41  }42  if (obj === null || (typeof obj !== 'object' && typeof obj !== 'function')) {43    return {default: obj};44  }45  var cache = _getRequireWildcardCache(nodeInterop);46  if (cache && cache.has(obj)) {47    return cache.get(obj);48  }49  var newObj = {};50  var hasPropertyDescriptor =51    Object.defineProperty && Object.getOwnPropertyDescriptor;52  for (var key in obj) {53    if (key !== 'default' && Object.prototype.hasOwnProperty.call(obj, key)) {54      var desc = hasPropertyDescriptor55        ? Object.getOwnPropertyDescriptor(obj, key)56        : null;57      if (desc && (desc.get || desc.set)) {58        Object.defineProperty(newObj, key, desc);59      } else {60        newObj[key] = obj[key];61      }62    }63  }64  newObj.default = obj;65  if (cache) {66    cache.set(obj, newObj);67  }68  return newObj;69}70/**71 * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.72 *73 * This source code is licensed under the MIT license found in the74 * LICENSE file in the root directory of this source tree.75 */76async function runGlobalHook({allTests, globalConfig, moduleName}) {77  const globalModulePaths = new Set(78    allTests.map(test => test.context.config[moduleName])79  );80  if (globalConfig[moduleName]) {81    globalModulePaths.add(globalConfig[moduleName]);82  }83  if (globalModulePaths.size > 0) {84    for (const modulePath of globalModulePaths) {85      if (!modulePath) {86        continue;87      }88      const correctConfig = allTests.find(89        t => t.context.config[moduleName] === modulePath90      );91      const projectConfig = correctConfig92        ? correctConfig.context.config // Fallback to first config93        : allTests[0].context.config;94      const transformer = await (0, _transform().createScriptTransformer)(95        projectConfig96      );97      try {98        await transformer.requireAndTranspileModule(99          modulePath,100          async globalModule => {101            if (typeof globalModule !== 'function') {102              throw new TypeError(103                `${moduleName} file must export a function at ${modulePath}`104              );105            }106            await globalModule(globalConfig);107          }108        );109      } catch (error) {110        if (util().types.isNativeError(error)) {111          error.message = `Jest: Got error running ${moduleName} - ${modulePath}, reason: ${error.message}`;112          throw error;113        }114        throw new Error(115          `Jest: Got error running ${moduleName} - ${modulePath}, reason: ${(0,116          _prettyFormat().default)(error, {117            maxDepth: 3118          })}`119        );120      }121    }122  }...

index.js

Source:index.js

1'use strict';2Object.defineProperty(exports, '__esModule', {3  value: true4});5Object.defineProperty(exports, 'createScriptTransformer', {6  enumerable: true,7  get: function () {8    return _ScriptTransformer.createScriptTransformer;9  }10});11Object.defineProperty(exports, 'createTranspilingRequire', {12  enumerable: true,13  get: function () {14    return _ScriptTransformer.createTranspilingRequire;15  }16});17Object.defineProperty(exports, 'handlePotentialSyntaxError', {18  enumerable: true,19  get: function () {20    return _enhanceUnexpectedTokenMessage.default;21  }22});23Object.defineProperty(exports, 'shouldInstrument', {24  enumerable: true,25  get: function () {26    return _shouldInstrument.default;27  }28});29var _ScriptTransformer = require('./ScriptTransformer');30var _shouldInstrument = _interopRequireDefault(require('./shouldInstrument'));31var _enhanceUnexpectedTokenMessage = _interopRequireDefault(32  require('./enhanceUnexpectedTokenMessage')33);34function _interopRequireDefault(obj) {35  return obj && obj.__esModule ? obj : {default: obj};...

Jest Testing Tutorial

LambdaTest’s Jest Testing Tutorial covers step-by-step guides around Jest with code examples to help you be proficient with the Jest framework. The Jest tutorial has chapters to help you learn right from the basics of Jest framework to code-based tutorials around testing react apps with Jest, perform snapshot testing, import ES modules and more.

Chapters

What is Jest Framework
Advantages of Jest - Jest has 3,898,000 GitHub repositories, as mentioned on its official website. Learn what makes Jest special and why Jest has gained popularity among the testing and developer community.
Jest Installation - All the prerequisites and set up steps needed to help you start Jest automation testing.
Using Jest with NodeJS Project - Learn how to leverage Jest framework to automate testing using a NodeJS Project.
Writing First Test for Jest Framework - Get started with code-based tutorial to help you write and execute your first Jest framework testing script.
Jest Vocabulary - Learn the industry renowned and official jargons of the Jest framework by digging deep into the Jest vocabulary.
Unit Testing with Jest - Step-by-step tutorial to help you execute unit testing with Jest framework.
Jest Basics - Learn about the most pivotal and basic features which makes Jest special.
Jest Parameterized Tests - Avoid code duplication and fasten automation testing with Jest using parameterized tests. Parameterization allows you to trigger the same test scenario over different test configurations by incorporating parameters.
Jest Matchers - Enforce assertions better with the help of matchers. Matchers help you compare the actual output with the expected one. Here is an example to see if the object is acquired from the correct class or not. -

|it('check_object_of_Car', () => { expect(newCar()).toBeInstanceOf(Car); });| | :- |

Jest Hooks: Setup and Teardown - Learn how to set up conditions which needs to be followed by the test execution and incorporate a tear down function to free resources after the execution is complete.
Jest Code Coverage - Unsure there is no code left unchecked in your application. Jest gives a specific flag called --coverage to help you generate code coverage.
HTML Report Generation - Learn how to create a comprehensive HTML report based on your Jest test execution.
Testing React app using Jest Framework - Learn how to test your react web-application with Jest framework in this detailed Jest tutorial.
Test using LambdaTest cloud Selenium Grid - Run your Jest testing script over LambdaTest cloud-based platform and leverage parallel testing to help trim down your test execution time.
Snapshot Testing for React Front Ends - Capture screenshots of your react based web-application and compare them automatically for visual anomalies with the help of Jest tutorial.
Bonus: Import ES modules with Jest - ES modules are also known as ECMAScript modules. Learn how to best use them by importing in your Jest testing scripts.
Jest vs Mocha vs Jasmine - Learn the key differences between the most popular JavaScript-based testing frameworks i.e. Jest, Mocha, and Jasmine.
Jest FAQs(Frequently Asked Questions) - Explore the most commonly asked questions around Jest framework, with their answers.