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.
29.0.0
[expect] [BREAKING] Differentiate between MatcherContext MatcherUtils and MatcherState types (#13141)[jest-circus] Add support for test.failing.each (#13142)[jest-config] [BREAKING] Make snapshotFormat default to escapeString: false and printBasicPrototype: false (#13036)[jest-config] [BREAKING] Remove undocumented collectCoverageOnlyFrom option (#13156)[jest-environment-jsdom] [BREAKING] Upgrade to jsdom@20 (#13037, #13058)[@jest/globals] Add jest.Mocked, jest.MockedClass, jest.MockedFunction and jest.MockedObject utility types (#12727)[jest-mock] [BREAKING] Refactor Mocked* utility types. MaybeMockedDeep and MaybeMocked became Mocked and MockedShallow respectively; only deep mocked variants of MockedClass, MockedFunction and MockedObject are exported (#13123, #13124)[jest-mock] [BREAKING] Change the default jest.mocked helper’s behavior to deep mocked (#13125)[jest-snapshot] [BREAKING] Let babel find config when updating inline snapshots (#13150)[@jest/test-result, @jest/types] [BREAKING] Replace Bytes and Milliseconds types with number (#13155)[jest-worker] Adds workerIdleMemoryLimit option which is used as a check for worker memory leaks >= Node 16.11.0 and recycles child workers as required (#13056, #13105, #13106, #13107)[pretty-format] [BREAKING] Remove ConvertAnsi plugin in favour of jest-serializer-ansi-escapes (#13040)[pretty-format] Allow to opt out from sorting object keys with compareKeys: null (#12443)[jest-config] Fix testing multiple projects with TypeScript config files (#13099)[@jest/expect-utils] Fix deep equality of ImmutableJS Record (#13055)[jest-haste-map] Increase the maximum possible file size that jest-haste-map can handle (#13094)[jest-runtime] Properly support CJS re-exports from dual packages (#13170)[jest-snapshot] Make prettierPath optional in SnapshotState (#13149)[jest-snapshot] Fix parsing error from inline snapshot files with JSX (#12760)[jest-worker] When a process runs out of memory worker exits correctly and doesn't spin indefinitely (#13054)[*] [BREAKING] Drop support for Node v12 and v17 (#13033)[docs] Fix webpack name (#13049)[docs] Explicit how to set n for --bail (#13128)[docs] Update Enzyme URL (#13166)[jest-leak-detector] Remove support for weak-napi (#13035)[jest-snapshot] [BREAKING] Require rootDir as argument to SnapshotState (#13150)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 18,158,643 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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