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How to use promisifyIt method in Jest

Best JavaScript code snippet using jest

jasmine_async.js

Source:jasmine_async.js

...13      return originalFn.call(env, fn, timeout);} // We make *all* functions async and run `done` right away if they14    // didn't return a promise.15    const asyncFn = function (done) {const returnValue = fn.call({});if (isPromise(returnValue)) {returnValue.then(done.bind(null, null), done.fail);} else {done();}};return originalFn.call(env, asyncFn, timeout);};} // Similar to promisifyLifeCycleFunction but throws an error16// when the return value is neither a Promise nor `undefined`...

jasmine-async.js

Source:jasmine-async.js

...14'use strict';15function isPromise(obj) {16  return obj && typeof obj.then === 'function';17}18// return a wrapping function: `env.fit = promisifyIt(env.it, env)`19function promisifyIt(originalFn, env) {20  return function (specName, fn, timeout) {21    if (!fn) {22      const spec = originalFn.call(env, specName);23      spec.pend('not implemented');24      return spec;25    }26    const isAsync = fn.length; // `done` was passed27    if (isAsync) {28      // jasmine will handle it29      return originalFn.call(env, specName, fn, timeout);30    } else {31      // we make *all* tests async and run `done` right away if they32      // didn't return a promise.33      return originalFn.call(env, specName, function (done) {34        const returnValue = fn.apply(this, arguments);35        if (isPromise(returnValue)) {36          returnValue.then(done).catch(done.fail);37        } else if (returnValue === undefined) {38          done();39        } else {40          done.fail(new Error(41          'Jest: `it` must return either a Promise or undefined.'));42        }43      }, timeout);44    }45  };46}47function promisifyLifeCycleFunction(originalFn, env) {48  return function (fn, timeout) {49    const hasDoneCallback = fn.length;50    if (!hasDoneCallback) {51      const originalBodyFn = fn;52      fn = function (done) {53        const returnValue = originalBodyFn.apply(this, arguments);54        if (isPromise(returnValue)) {55          returnValue.then(done, done.fail);56        } else {57          done();58        }59      };60    }61    return originalFn.call(env, fn, timeout);62  };63}64function makeConcurrent(originalFn, env) {65  return function (specName, fn, timeout) {66    let promise;67    try {68      promise = fn();69      if (!isPromise(promise)) {70        throw new Error('Jest: concurrent tests must return a Promise.');71      }72    } catch (error) {73      return originalFn.call(env, Promise.reject(error));74    }75    return originalFn.call(env, specName, () => promise, timeout);76  };77}78function install(global) {79  const jasmine = global.jasmine;80  const env = jasmine.getEnv();81  global.pit = env.it = promisifyIt(env.it, env);82  env.fit = promisifyIt(env.fit, env);83  global.it.concurrent = makeConcurrent(env.it, env);84  global.it.concurrent.only = makeConcurrent(env.fit, env);85  global.it.concurrent.skip = makeConcurrent(env.xit, env);86  global.fit.concurrent = makeConcurrent(env.fit);87  env.afterAll = promisifyLifeCycleFunction(env.afterAll, env);88  env.afterEach = promisifyLifeCycleFunction(env.afterEach, env);89  env.beforeAll = promisifyLifeCycleFunction(env.beforeAll, env);90  env.beforeEach = promisifyLifeCycleFunction(env.beforeEach, env);91}92module.exports = {...

jasmine-pit.js

Source:jasmine-pit.js

...12'use strict';13function isPromise(obj) {14  return obj && typeof obj.then === 'function';15}16// return a wrapping function: `env.fit = promisifyIt(env.it, env)`17function promisifyIt(originalFn, env) {18  return function(specName, fn) {19    if (!fn) {20      return null;21    }22    const isAsync = fn.length; // `done` was passed23    if (isAsync) {24      return originalFn.call(env, specName, fn); // jasmine will handle it25    } else {26      // we make *all* tests async and run `done` right away if they27      // didn't return a promise.28      return originalFn.call(env, specName, function(done) {29        const returnValue = fn.apply(this, arguments);30        if (isPromise(returnValue)) {31          returnValue.then(done).catch(done.fail);32        } else if (returnValue === undefined) {33          done();34        } else {35          done.fail(new Error(36            'Jest: `it` must return either a Promise or undefined.'37          ));38        }39      });40    }41  };42}43function install(global) {44  const jasmine = global.jasmine;45  const env = jasmine.getEnv();46  global.pit = env.it = promisifyIt(env.it, env);47  env.fit = promisifyIt(env.fit, env);48}49module.exports = {50  install,...

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.