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This package exports the `expect` function used in [Jest](https://jestjs.io/). You can find its documentation [on Jest's website](https://jestjs.io/docs/expect).
The 'expect' npm package is a library for writing test assertions. It is commonly used in conjunction with testing frameworks like Jest or Mocha to validate the behavior of JavaScript code. It provides a range of assertion types and matchers that allow developers to write expressive and readable tests.
Basic Assertions
This feature allows you to assert that a value matches exactly what you expect. The 'toBe' matcher compares with ===.
expect(2 + 2).toBe(4);
Object Property Assertions
With this feature, you can assert that an object has a specific property with a certain value. The 'toHaveProperty' matcher checks for the existence and value of a property in an object.
expect({ name: 'Alice', age: 30 }).toHaveProperty('name', 'Alice');
Exception Testing
This feature is used to test if a function throws an exception when it is executed. The 'toThrow' matcher is used to assert that an error is thrown with a specific message.
expect(() => { throw new Error('failure'); }).toThrow('failure');
Array Containment
This feature allows you to assert that an array contains a specific item. The 'toContain' matcher checks if an array includes the expected item.
expect(['Alice', 'Bob', 'Eve']).toContain('Bob');
Asynchronous Assertions
This feature enables you to write assertions for asynchronous code. The 'resolves' matcher waits for a promise to resolve and then checks the resolved value.
expect(Promise.resolve('success')).resolves.toBe('success');
Chai is a BDD/TDD assertion library for node and the browser that can be paired with any javascript testing framework. It offers a similar range of matchers and assertions as expect, and it provides a fluent chainable language to construct assertions.
Should.js is an expressive, readable, framework-agnostic assertion library. The key difference is in the style of assertions it offers, using a more fluent chainable API that reads like English.
Assert is a module that provides a set of assertion functions for verifying invariants. It is built into Node.js and is less feature-rich compared to expect, but it serves as a simple way to write assertions in a Node.js environment.
Jest is a delightful JavaScript Testing Framework with a focus on simplicity. It comes with its own assertion library, which provides functionality similar to expect, as expect is actually part of Jest.
This package exports the expect
function used in Jest. You can find its documentation on Jest's website.
27.4.0
[expect]
Enhancing the toHaveProperty
matcher to support array selection (#12092)[jest-core]
Add support for testResultsProcessor
written in ESM (#12006)[jest-diff, pretty-format]
Add compareKeys
option for custom sorting of object keys (#11992)[jest-mock]
Add ts-jest
mock util functions (#12089)[expect]
Allow again expect.Matchers
generic with single value (#11986)[jest-circus, jest-jasmine2]
Avoid false concurrent test failures due to unhandled promise rejections (#11987)[jest-config]
Add missing slash
dependency to package.json
(#12080)[jest-core]
Incorrect detection of open ZLIB handles (#12022)[jest-diff]
Break dependency cycle (#10818)[jest-environment-jsdom]
Add @types/jsdom
dependency (#11999)[jest-environment-jsdom]
Do not reset the global.document too early on teardown (#11871)[jest-transform]
Improve error and warning messages (#11998)[jest-worker]
Pass execArgv
correctly to worker_threads
worker (#12069)FAQs
This package exports the `expect` function used in [Jest](https://jestjs.io/). You can find its documentation [on Jest's website](https://jestjs.io/docs/expect).
The npm package expect receives a total of 23,663,066 weekly downloads. As such, expect popularity was classified as popular.
We found that expect demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 2 open source maintainers collaborating on the project.
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