How to use takesDoneCallback method in Jest

Best JavaScript code snippet using jest


Source:utils.js Github


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...144});145const jestEachBuildDir = (0, _slash.default)(146 path.dirname(require.resolve('jest-each'))147);148function takesDoneCallback(fn) {149 return fn.length > 0;150}151function isGeneratorFunction(fn) {152 return (0, _isGeneratorFn.default)(fn);153}154const makeDescribe = (name, parent, mode) => {155 let _mode = mode;156 if (parent && !mode) {157 // If not set explicitly, inherit from the parent describe.158 _mode = parent.mode;159 }160 return {161 type: 'describeBlock',162 // eslint-disable-next-line sort-keys163 children: [],164 hooks: [],165 mode: _mode,166 name: (0, _jestUtil.convertDescriptorToString)(name),167 parent,168 tests: []169 };170};171exports.makeDescribe = makeDescribe;172const makeTest = (fn, mode, name, parent, timeout, asyncError) => ({173 type: 'test',174 // eslint-disable-next-line sort-keys175 asyncError,176 duration: null,177 errors: [],178 fn,179 invocations: 0,180 mode,181 name: (0, _jestUtil.convertDescriptorToString)(name),182 parent,183 seenDone: false,184 startedAt: null,185 status: null,186 timeout187}); // Traverse the tree of describe blocks and return true if at least one describe188// block has an enabled test.189exports.makeTest = makeTest;190const hasEnabledTest = describeBlock => {191 const {hasFocusedTests, testNamePattern} = (0, _state.getState)();192 return describeBlock.children.some(child =>193 child.type === 'describeBlock'194 ? hasEnabledTest(child)195 : !(196 child.mode === 'skip' ||197 (hasFocusedTests && child.mode !== 'only') ||198 (testNamePattern && !testNamePattern.test(getTestID(child)))199 )200 );201};202const getAllHooksForDescribe = describe => {203 const result = {204 afterAll: [],205 beforeAll: []206 };207 if (hasEnabledTest(describe)) {208 for (const hook of describe.hooks) {209 switch (hook.type) {210 case 'beforeAll':211 result.beforeAll.push(hook);212 break;213 case 'afterAll':214 result.afterAll.push(hook);215 break;216 }217 }218 }219 return result;220};221exports.getAllHooksForDescribe = getAllHooksForDescribe;222const getEachHooksForTest = test => {223 const result = {224 afterEach: [],225 beforeEach: []226 };227 let block = test.parent;228 do {229 const beforeEachForCurrentBlock = []; // TODO: inline after is released230 let hook;231 for (hook of block.hooks) {232 switch (hook.type) {233 case 'beforeEach':234 beforeEachForCurrentBlock.push(hook);235 break;236 case 'afterEach':237 result.afterEach.push(hook);238 break;239 }240 } // 'beforeEach' hooks are executed from top to bottom, the opposite of the241 // way we traversed it.242 result.beforeEach = [...beforeEachForCurrentBlock, ...result.beforeEach];243 } while ((block = block.parent));244 return result;245};246exports.getEachHooksForTest = getEachHooksForTest;247const describeBlockHasTests = describe =>248 describe.children.some(249 child => child.type === 'test' || describeBlockHasTests(child)250 );251exports.describeBlockHasTests = describeBlockHasTests;252const _makeTimeoutMessage = (timeout, isHook) =>253 `Exceeded timeout of ${(0, _jestUtil.formatTime)(timeout)} for a ${254 isHook ? 'hook' : 'test'255 }.\nUse jest.setTimeout(newTimeout) to increase the timeout value, if this is a long-running test.`; // Global values can be overwritten by mocks or tests. We'll capture256// the original values in the variables before we require any files.257const {setTimeout, clearTimeout} = global;258function checkIsError(error) {259 return !!(error && error.message && error.stack);260}261const callAsyncCircusFn = (testOrHook, testContext, {isHook, timeout}) => {262 let timeoutID;263 let completed = false;264 const {fn, asyncError} = testOrHook;265 return new Promise((resolve, reject) => {266 timeoutID = setTimeout(267 () => reject(_makeTimeoutMessage(timeout, isHook)),268 timeout269 ); // If this fn accepts `done` callback we return a promise that fulfills as270 // soon as `done` called.271 if (takesDoneCallback(fn)) {272 let returnedValue = undefined;273 const done = reason => {274 // We need to keep a stack here before the promise tick275 const errorAtDone = new _jestUtil.ErrorWithStack(undefined, done);276 if (!completed && testOrHook.seenDone) {277 errorAtDone.message =278 'Expected done to be called once, but it was called multiple times.';279 if (reason) {280 errorAtDone.message +=281 ' Reason: ' +282 (0, _prettyFormat.format)(reason, {283 maxDepth: 3284 });285 }...

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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.
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  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.
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  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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