How to use replaceMatchedToAsymmetricMatcher method in Jest

Best JavaScript code snippet using jest


Source:index.js Github


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...320 return expectedLine + '\n' + receivedLine;321 }322 if (isLineDiffable(expected, received)) {323 const {replacedExpected, replacedReceived} =324 replaceMatchedToAsymmetricMatcher(325 (0, _deepCyclicCopyReplaceable.default)(expected),326 (0, _deepCyclicCopyReplaceable.default)(received),327 [],328 []329 );330 const difference = (0, _jestDiff.diff)(replacedExpected, replacedReceived, {331 aAnnotation: expectedLabel,332 bAnnotation: receivedLabel,333 expand,334 includeChangeCounts: true335 });336 if (337 typeof difference === 'string' &&338 difference.includes('- ' + expectedLabel) &&339 difference.includes('+ ' + receivedLabel)340 ) {341 return difference;342 }343 }344 const printLabel = getLabelPrinter(expectedLabel, receivedLabel);345 const expectedLine = printLabel(expectedLabel) + printExpected(expected);346 const receivedLine =347 printLabel(receivedLabel) +348 (stringify(expected) === stringify(received)349 ? 'serializes to the same string'350 : printReceived(received));351 return expectedLine + '\n' + receivedLine;352}; // Sometimes, e.g. when comparing two numbers, the output from jest-diff353// does not contain more information than the `Expected:` / `Received:` already gives.354// In those cases, we do not print a diff to make the output shorter and not redundant.355exports.printDiffOrStringify = printDiffOrStringify;356const shouldPrintDiff = (actual, expected) => {357 if (typeof actual === 'number' && typeof expected === 'number') {358 return false;359 }360 if (typeof actual === 'bigint' && typeof expected === 'bigint') {361 return false;362 }363 if (typeof actual === 'boolean' && typeof expected === 'boolean') {364 return false;365 }366 return true;367};368function replaceMatchedToAsymmetricMatcher(369 replacedExpected,370 replacedReceived,371 expectedCycles,372 receivedCycles373) {374 if (!_Replaceable.default.isReplaceable(replacedExpected, replacedReceived)) {375 return {376 replacedExpected,377 replacedReceived378 };379 }380 if (381 expectedCycles.includes(replacedExpected) ||382 receivedCycles.includes(replacedReceived)383 ) {384 return {385 replacedExpected,386 replacedReceived387 };388 }389 expectedCycles.push(replacedExpected);390 receivedCycles.push(replacedReceived);391 const expectedReplaceable = new _Replaceable.default(replacedExpected);392 const receivedReplaceable = new _Replaceable.default(replacedReceived);393 expectedReplaceable.forEach((expectedValue, key) => {394 const receivedValue = receivedReplaceable.get(key);395 if (isAsymmetricMatcher(expectedValue)) {396 if (expectedValue.asymmetricMatch(receivedValue)) {397 receivedReplaceable.set(key, expectedValue);398 }399 } else if (isAsymmetricMatcher(receivedValue)) {400 if (receivedValue.asymmetricMatch(expectedValue)) {401 expectedReplaceable.set(key, receivedValue);402 }403 } else if (404 _Replaceable.default.isReplaceable(expectedValue, receivedValue)405 ) {406 const replaced = replaceMatchedToAsymmetricMatcher(407 expectedValue,408 receivedValue,409 expectedCycles,410 receivedCycles411 );412 expectedReplaceable.set(key, replaced.replacedExpected);413 receivedReplaceable.set(key, replaced.replacedReceived);414 }415 });416 return {417 replacedExpected: expectedReplaceable.object,418 replacedReceived: receivedReplaceable.object419 };420}...

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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.


  1. What is Jest Framework
  2. 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.
  3. Jest Installation - All the prerequisites and set up steps needed to help you start Jest automation testing.
  4. Using Jest with NodeJS Project - Learn how to leverage Jest framework to automate testing using a NodeJS Project.
  5. Writing First Test for Jest Framework - Get started with code-based tutorial to help you write and execute your first Jest framework testing script.
  6. Jest Vocabulary - Learn the industry renowned and official jargons of the Jest framework by digging deep into the Jest vocabulary.
  7. Unit Testing with Jest - Step-by-step tutorial to help you execute unit testing with Jest framework.
  8. Jest Basics - Learn about the most pivotal and basic features which makes Jest special.
  9. 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.
  10. 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. -

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

  1. 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.
  2. 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.
  3. HTML Report Generation - Learn how to create a comprehensive HTML report based on your Jest test execution.
  4. Testing React app using Jest Framework - Learn how to test your react web-application with Jest framework in this detailed Jest tutorial.
  5. 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.
  6. 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.
  7. 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.
  8. Jest vs Mocha vs Jasmine - Learn the key differences between the most popular JavaScript-based testing frameworks i.e. Jest, Mocha, and Jasmine.
  9. Jest FAQs(Frequently Asked Questions) - Explore the most commonly asked questions around Jest framework, with their answers.

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