Best JavaScript code snippet using jest
formatNodeAssertErrors.js
Source: formatNodeAssertErrors.js
...120 .replace(message, '')121 .replace(/AssertionError(.*)/g, '');122 if (operatorName === 'doesNotThrow') {123 return (124 buildHintString(assertThrowingMatcherHint(operatorName)) +125 _chalk.default.reset(`Expected the function not to throw an error.\n`) +126 _chalk.default.reset(`Instead, it threw:\n`) +127 ` ${(0, _jestMatcherUtils.printReceived)(actual)}` +128 _chalk.default.reset(129 hasCustomMessage ? '\n\nMessage:\n ' + message : ''130 ) +131 trimmedStack132 );133 }134 if (operatorName === 'throws') {135 return (136 buildHintString(assertThrowingMatcherHint(operatorName)) +137 _chalk.default.reset(`Expected the function to throw an error.\n`) +138 _chalk.default.reset(`But it didn't throw anything.`) +139 _chalk.default.reset(140 hasCustomMessage ? '\n\nMessage:\n ' + message : ''141 ) +142 trimmedStack143 );144 }145 if (operatorName === 'fail') {146 return (147 buildHintString(assertMatcherHint(operator, operatorName, expected)) +148 _chalk.default.reset(hasCustomMessage ? 'Message:\n ' + message : '') +149 trimmedStack150 );151 }152 return (153 buildHintString(assertMatcherHint(operator, operatorName, expected)) +154 _chalk.default.reset(`Expected value ${operatorMessage(operator)}`) +155 ` ${(0, _jestMatcherUtils.printExpected)(expected)}\n` +156 _chalk.default.reset(`Received:\n`) +157 ` ${(0, _jestMatcherUtils.printReceived)(actual)}` +158 _chalk.default.reset(hasCustomMessage ? '\n\nMessage:\n ' + message : '') +159 (diffString ? `\n\nDifference:\n\n${diffString}` : '') +160 trimmedStack161 );162}163function isAssertionError(error) {164 return (165 error &&166 (error instanceof _assert.AssertionError ||167 error.name === _assert.AssertionError.name ||168 error.code === 'ERR_ASSERTION')169 );170}171function buildHintString(hint) {172 return hint ? hint + '\n\n' : '';173}174var _default = formatNodeAssertErrors;...
assertionErrorMessage.js
Source: assertionErrorMessage.js
...87 .replace(message, '')88 .replace(/AssertionError(.*)/g, '');89 if (operatorName === 'doesNotThrow') {90 return (91 buildHintString(assertThrowingMatcherHint(operatorName)) +92 _chalk.default.reset(`Expected the function not to throw an error.\n`) +93 _chalk.default.reset(`Instead, it threw:\n`) +94 ` ${(0, _jestMatcherUtils.printReceived)(actual)}` +95 _chalk.default.reset(96 hasCustomMessage ? '\n\nMessage:\n ' + message : ''97 ) +98 trimmedStack99 );100 }101 if (operatorName === 'throws') {102 return (103 buildHintString(assertThrowingMatcherHint(operatorName)) +104 _chalk.default.reset(`Expected the function to throw an error.\n`) +105 _chalk.default.reset(`But it didn't throw anything.`) +106 _chalk.default.reset(107 hasCustomMessage ? '\n\nMessage:\n ' + message : ''108 ) +109 trimmedStack110 );111 }112 if (operatorName === 'fail') {113 return (114 buildHintString(assertMatcherHint(operator, operatorName, expected)) +115 _chalk.default.reset(hasCustomMessage ? 'Message:\n ' + message : '') +116 trimmedStack117 );118 }119 return (120 buildHintString(assertMatcherHint(operator, operatorName, expected)) +121 _chalk.default.reset(`Expected value ${operatorMessage(operator)}`) +122 ` ${(0, _jestMatcherUtils.printExpected)(expected)}\n` +123 _chalk.default.reset(`Received:\n`) +124 ` ${(0, _jestMatcherUtils.printReceived)(actual)}` +125 _chalk.default.reset(hasCustomMessage ? '\n\nMessage:\n ' + message : '') +126 (diffString ? `\n\nDifference:\n\n${diffString}` : '') +127 trimmedStack128 );129}130function buildHintString(hint) {131 return hint ? hint + '\n\n' : '';132}133var _default = assertionErrorMessage;...
How to test if a method returns an array of a class in Jest
How do node_modules packages read config files in the project root?
Jest: how to mock console when it is used by a third-party-library?
ERESOLVE unable to resolve dependency tree while installing a pacakge
Testing arguments with toBeCalledWith() in Jest
Is there assertCountEqual equivalent in javascript unittests jest library?
NodeJS: NOT able to set PERCY_TOKEN via package script with start-server-and-test
Jest: How to consume result of jest.genMockFromModule
How To Reset Manual Mocks In Jest
How to move '__mocks__' folder in Jest to /test?
Since Jest tests are runtime tests, they only have access to runtime information. You're trying to use a type, which is compile-time information. TypeScript should already be doing the type aspect of this for you. (More on that in a moment.)
The fact the tests only have access to runtime information has a couple of ramifications:
If it's valid for getAll
to return an empty array (because there aren't any entities to get), the test cannot tell you whether the array would have had Entity
elements in it if it hadn't been empty. All it can tell you is it got an array.
In the non-empty case, you have to check every element of the array to see if it's an Entity
. You've said Entity
is a class, not just a type, so that's possible. I'm not a user of Jest (I should be), but it doesn't seem to have a test specifically for this; it does have toBeTruthy
, though, and we can use every
to tell us if every element is an Entity
:
it('should return an array of Entity class', async () => {
const all = await service.getAll()
expect(all.every(e => e instanceof Entity)).toBeTruthy();
});
Beware, though, that all calls to every
on an empty array return true
, so again, that empty array issue raises its head.
If your Jest tests are written in TypeScript, you can improve on that by ensuring TypeScript tests the compile-time type of getAll
's return value:
it('should return an array of Entity class', async () => {
const all: Entity[] = await service.getAll()
// ^^^^^^^^^^
expect(all.every(e => e instanceof Entity)).toBeTruthy();
});
TypeScript will complain about that assignment at compile time if it's not valid, and Jest will complain at runtime if it sees an array containing a non-Entity
object.
But jonrsharpe has a good point: This test may not be useful vs. testing for specific values that should be there.
Check out the latest blogs from LambdaTest on this topic:
Node js has become one of the most popular frameworks in JavaScript today. Used by millions of developers, to develop thousands of project, node js is being extensively used. The more you develop, the better the testing you require to have a smooth, seamless application. This article shares the best practices for the testing node.in 2019, to deliver a robust web application or website.
Storybook offers a clean-room setting for isolating component testing. No matter how complex a component is, stories make it simple to explore it in all of its permutations. Before we discuss the Storybook testing in any browser, let us try and understand the fundamentals related to the Storybook framework and how it simplifies how we build UI components.
Quality Assurance (QA) is at the point of inflection and it is an exciting time to be in the field of QA as advanced digital technologies are influencing QA practices. As per a press release by Gartner, The encouraging part is that IT and automation will play a major role in transformation as the IT industry will spend close to $3.87 trillion in 2020, up from $3.76 trillion in 2019.
This article is a part of our Content Hub. For more in-depth resources, check out our content hub on WebDriverIO Tutorial and Selenium JavaScript Tutorial.
Having a strategy or plan can be the key to unlocking many successes, this is true to most contexts in life whether that be sport, business, education, and much more. The same is true for any company or organisation that delivers software/application solutions to their end users/customers. If you narrow that down even further from Engineering to Agile and then even to Testing or Quality Engineering, then strategy and planning is key at every level.
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.
|<p>it('check_object_of_Car', () => {</p><p>
expect(newCar()).toBeInstanceOf(Car);</p><p>
});</p>|
| :- |
Get 100 minutes of automation test minutes FREE!!