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|---|---|---|
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| <h1 align="center">jest-fixed-jsdom</h1> | ||
| <p align="center">This library helps re-attach missing NodeJS globals definitions in JSDOM that Jest strips out</p> | ||
| <p align="center">A superset of the JSDOM environment for Jest that respects Node.js globals.</p> | ||
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| ## Motivation | ||
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| Jest strips out a number of NodeJS globals that are used in tests and libraries involving JSDOM, such as structuredClone, ReadableStream, and so on. This library patches these globals back in - there is no polyfilling or mocking involved, it simply re-attaches the missing globals to the JSDOM environment. If you've ever come across errors such as `ReferenceError: ReadableStream is not defined` or `ReferenceError: structuredClone is not defined`, this library is for you. If you were previously using (undici)[https://www.npmjs.com/package/undici] purely to solve this, you will no longer need it. | ||
| When you use Jest with JSDOM you are getting a broken test environment. Some Node.js globals cease to exist (e.g. `Request`, `Response`, `TextEncoder`, `TextDecoder`, `ReadableStream`<sup><a href="https://github.com/mswjs/msw/issues/1916">1</a></sup>), while others stop behaving correctly (e.g. `Event`, `MessageEvent`<sup><a href="https://github.com/nodejs/undici/issues/2663">2</a></sup>, `structuredClone()`<sup><a href="https://github.com/mswjs/msw/issues/1931">3</a></sup>). That is caused by `jest-environment-jsdom` and JSDOM relying on polyfills to implement standard APIs that have been available globally both in the browser and in Node.js for years. | ||
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| ## Installation | ||
| Here's a piece of valid JavaScript that works in both the browser and Node.js but fails in Jest/JSDOM: | ||
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| `npm install jest-fixed-jsdom -D` | ||
| ```js | ||
| new TextEncoder().encode('hello') | ||
| ``` | ||
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| ``` | ||
| ReferenceError: TextEncoder is not defined | ||
| ``` | ||
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| **We strongly believe that a valid JavaScript code must compile regardless of what test environment you are using**. In fact, having a proper test environment is crucial to get any kind of value from your tests. Jest/JSDOM take that already working environment away from you. | ||
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| We've built this project aims to fix that problem, restoring the global APIs that are present in both environments, providing better interoperability, stability, and consistent runtime behavior. | ||
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| ## Changes | ||
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| ## Configuring your jest environment to use jest-fixed-jsdom | ||
| This project "fixes" the following global APIs, overriding whichever polyfills they have with respective Node.js globals: | ||
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| You will need to add/modify two properties in your jest configuration to use jest-fixed-jsdom. | ||
| - `EventTarget` | ||
| - `Event` | ||
| - `MessageEvent` | ||
| - `fetch()` | ||
| - `Blob` | ||
| - `FormData` | ||
| - `Headers` | ||
| - `Request` | ||
| - `Response` | ||
| - `ReadableStream` | ||
| - `TextEncoder` | ||
| - `TextDecoder` | ||
| - `structuredClone()` | ||
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| ## Getting started | ||
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| ### Install | ||
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| ```sh | ||
| npm i jest-fixed-jsdom --save-dev | ||
| ``` | ||
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| ### Configure Jest | ||
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| In your `jest.config.js`, set the `testEnvironment` option to `jest-fixed-jsdom`: | ||
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| ```json | ||
| // jest.config.js | ||
| { | ||
| "testEnvironment": "jest-fixed-jsdom" | ||
| } | ||
| ``` | ||
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| Setting `testEnvironment` to `jest-fixed-jsdom` will tell Jest to use jest-fixed-jsdom as the test environment. Setting `customExportConditions` to an empty array will stop JSDOM from using the browser environment to load exports. | ||
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| > You can use any other `testEnvironmentOptions` you need. Those will be forwarded to the underlying `jest-environment-jsdom`. |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,151 +1,153 @@ | ||
| test('exposes "Blob"', async () => { | ||
| expect(globalThis).toHaveProperty('Blob') | ||
| expect(() => new Blob()).not.toThrow() | ||
| await expect(new Blob(['hello']).text()).resolves.toBe('hello') | ||
| }) | ||
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| test('exposes "TextEncoder"', () => { | ||
| expect(globalThis).toHaveProperty('TextEncoder') | ||
| expect(() => new TextEncoder()).not.toThrow() | ||
| expect(Buffer.from(new TextEncoder().encode('hello'))).toEqual( | ||
| Buffer.from(new Uint8Array([104, 101, 108, 108, 111])), | ||
| ) | ||
| }) | ||
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| test('exposes "TextDecoder"', () => { | ||
| expect(globalThis).toHaveProperty('TextDecoder') | ||
| expect(() => new TextDecoder()).not.toThrow() | ||
| expect( | ||
| new TextDecoder().decode(new Uint8Array([104, 101, 108, 108, 111])), | ||
| ).toBe('hello') | ||
| }) | ||
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| test('exposes "ReadableStream"', () => { | ||
| expect(globalThis).toHaveProperty('ReadableStream') | ||
| expect(() => new ReadableStream()).not.toThrow() | ||
| }) | ||
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| test('exposes "Headers"', () => { | ||
| expect(globalThis).toHaveProperty('Headers') | ||
| expect(() => new Headers()).not.toThrow() | ||
| expect(new Headers([['a', 'b']]).get('a')).toBe('b') | ||
| }) | ||
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| test('exposes "FormData"', () => { | ||
| expect(globalThis).toHaveProperty('FormData') | ||
| expect(() => new FormData()).not.toThrow() | ||
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| const data = new FormData() | ||
| data.set('a', 'b') | ||
| expect(data.get('a')).toBe('b') | ||
| }) | ||
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| test('exposes "Request"', async () => { | ||
| expect(globalThis).toHaveProperty('Request') | ||
| expect(() => new Request('https://example.com')).not.toThrow() | ||
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| const request = new Request('https://example.com', { | ||
| method: 'POST', | ||
| body: 'hello world', | ||
| }) | ||
| expect(await request.text()).toBe('hello world') | ||
| }) | ||
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| test('exposes "Response"', async () => { | ||
| expect(globalThis).toHaveProperty('Response') | ||
| expect(() => new Response('hello')).not.toThrow() | ||
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| const response = new Response('hello') | ||
| expect(await response.text()).toBe('hello') | ||
| }) | ||
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| test('exposes "structuredClone"', async () => { | ||
| expect(globalThis).toHaveProperty('structuredClone') | ||
| expect(() => structuredClone('hello')).not.toThrow() | ||
| expect(structuredClone('hello')).toBe('hello') | ||
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| const stream = new ReadableStream({ | ||
| start(controller) { | ||
| controller.enqueue('hello') | ||
| controller.close() | ||
| }, | ||
| }) | ||
| /** | ||
| * @note Jest/JSDOM failes cloning ReadableStream because they use | ||
| * "core-js" to polyfill "structuredClone()" and it doesn't support it. | ||
| * @see https://github.com/mswjs/msw/issues/1929#issuecomment-1908535966 | ||
| */ | ||
| const clone = structuredClone(stream, { transfer: [stream] }) | ||
| expect(clone).toBeInstanceOf(ReadableStream) | ||
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| const chunks = [] | ||
| const reader = clone.getReader() | ||
| while (true) { | ||
| const { done, value } = await reader.read() | ||
| if (done) break | ||
| chunks.push(value) | ||
| } | ||
| expect(chunks).toEqual(['hello']) | ||
| }) | ||
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| test('exposes "EventTarget"', () => { | ||
| expect(globalThis).toHaveProperty('EventTarget') | ||
| expect(() => new EventTarget()).not.toThrow() | ||
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| const target = new EventTarget() | ||
| const symbols = Object.getOwnPropertySymbols(target).map( | ||
| (symbol) => symbol.description, | ||
| ) | ||
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| // EventTarget must not be implemented by JSDOM. | ||
| expect(symbols).not.toContain('impl') | ||
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| // In Node.js, EventTarget keeps events behind the kEvents symbol. | ||
| expect(symbols).toContain('kEvents') | ||
| }) | ||
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| test('exposes "Event"', () => { | ||
| expect(globalThis).toHaveProperty('Event') | ||
| expect(() => new Event('click')).not.toThrow() | ||
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| const event = new Event('click') | ||
| const symbols = Object.getOwnPropertySymbols(event).map( | ||
| (symbol) => symbol.description, | ||
| ) | ||
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| // The "impl" symbol is added by JSDOM. | ||
| expect(symbols).not.toContain('impl') | ||
| // Node.js expects events to have the "type" symbol. | ||
| expect(symbols).toContain('type') | ||
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| /** | ||
| * Perform a basic "isEvent()" check that Node.js has. | ||
| * @see https://github.com/nodejs/node/blob/3a456c6db802b5b25594d3a9d235d4989e9f7829/lib/internal/event_target.js#L96 | ||
| */ | ||
| expect(event[symbols.find((description) => description === 'type')]).toBe( | ||
| 'click', | ||
| ) | ||
| }) | ||
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| test('exposes "MessageEvent"', () => { | ||
| expect(globalThis).toHaveProperty('MessageEvent') | ||
| expect(() => new MessageEvent('click')).not.toThrow() | ||
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| const event = new MessageEvent('message') | ||
| const symbols = Object.getOwnPropertySymbols(event).map( | ||
| (symbol) => symbol.description, | ||
| ) | ||
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| // The "impl" symbol is added by JSDOM. | ||
| expect(symbols).not.toContain('impl') | ||
| // Node.js expects events to have the "type" symbol. | ||
| expect(symbols).toContain('type') | ||
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| /** | ||
| * Perform a basic "isEvent()" check that Node.js has. | ||
| * @see https://github.com/nodejs/node/blob/3a456c6db802b5b25594d3a9d235d4989e9f7829/lib/internal/event_target.js#L96 | ||
| */ | ||
| expect(event[symbols.find((description) => description === 'type')]).toBe( | ||
| 'message', | ||
| ) | ||
| }) | ||
| new TextEncoder().encode('hello') | ||
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| // test('exposes "Blob"', async () => { | ||
| // expect(globalThis).toHaveProperty('Blob') | ||
| // expect(() => new Blob()).not.toThrow() | ||
| // await expect(new Blob(['hello']).text()).resolves.toBe('hello') | ||
| // }) | ||
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| // test('exposes "TextEncoder"', () => { | ||
| // expect(globalThis).toHaveProperty('TextEncoder') | ||
| // expect(() => new TextEncoder()).not.toThrow() | ||
| // expect(Buffer.from(new TextEncoder().encode('hello'))).toEqual( | ||
| // Buffer.from(new Uint8Array([104, 101, 108, 108, 111])), | ||
| // ) | ||
| // }) | ||
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| // test('exposes "TextDecoder"', () => { | ||
| // expect(globalThis).toHaveProperty('TextDecoder') | ||
| // expect(() => new TextDecoder()).not.toThrow() | ||
| // expect( | ||
| // new TextDecoder().decode(new Uint8Array([104, 101, 108, 108, 111])), | ||
| // ).toBe('hello') | ||
| // }) | ||
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| // test('exposes "ReadableStream"', () => { | ||
| // expect(globalThis).toHaveProperty('ReadableStream') | ||
| // expect(() => new ReadableStream()).not.toThrow() | ||
| // }) | ||
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| // test('exposes "Headers"', () => { | ||
| // expect(globalThis).toHaveProperty('Headers') | ||
| // expect(() => new Headers()).not.toThrow() | ||
| // expect(new Headers([['a', 'b']]).get('a')).toBe('b') | ||
| // }) | ||
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| // test('exposes "FormData"', () => { | ||
| // expect(globalThis).toHaveProperty('FormData') | ||
| // expect(() => new FormData()).not.toThrow() | ||
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| // const data = new FormData() | ||
| // data.set('a', 'b') | ||
| // expect(data.get('a')).toBe('b') | ||
| // }) | ||
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| // test('exposes "Request"', async () => { | ||
| // expect(globalThis).toHaveProperty('Request') | ||
| // expect(() => new Request('https://example.com')).not.toThrow() | ||
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| // const request = new Request('https://example.com', { | ||
| // method: 'POST', | ||
| // body: 'hello world', | ||
| // }) | ||
| // expect(await request.text()).toBe('hello world') | ||
| // }) | ||
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| // test('exposes "Response"', async () => { | ||
| // expect(globalThis).toHaveProperty('Response') | ||
| // expect(() => new Response('hello')).not.toThrow() | ||
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| // const response = new Response('hello') | ||
| // expect(await response.text()).toBe('hello') | ||
| // }) | ||
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| // test('exposes "structuredClone"', async () => { | ||
| // expect(globalThis).toHaveProperty('structuredClone') | ||
| // expect(() => structuredClone('hello')).not.toThrow() | ||
| // expect(structuredClone('hello')).toBe('hello') | ||
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| // const stream = new ReadableStream({ | ||
| // start(controller) { | ||
| // controller.enqueue('hello') | ||
| // controller.close() | ||
| // }, | ||
| // }) | ||
| // /** | ||
| // * @note Jest/JSDOM failes cloning ReadableStream because they use | ||
| // * "core-js" to polyfill "structuredClone()" and it doesn't support it. | ||
| // * @see https://github.com/mswjs/msw/issues/1929#issuecomment-1908535966 | ||
| // */ | ||
| // const clone = structuredClone(stream, { transfer: [stream] }) | ||
| // expect(clone).toBeInstanceOf(ReadableStream) | ||
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| // const chunks = [] | ||
| // const reader = clone.getReader() | ||
| // while (true) { | ||
| // const { done, value } = await reader.read() | ||
| // if (done) break | ||
| // chunks.push(value) | ||
| // } | ||
| // expect(chunks).toEqual(['hello']) | ||
| // }) | ||
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| // test('exposes "EventTarget"', () => { | ||
| // expect(globalThis).toHaveProperty('EventTarget') | ||
| // expect(() => new EventTarget()).not.toThrow() | ||
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| // const target = new EventTarget() | ||
| // const symbols = Object.getOwnPropertySymbols(target).map( | ||
| // (symbol) => symbol.description, | ||
| // ) | ||
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| // // EventTarget must not be implemented by JSDOM. | ||
| // expect(symbols).not.toContain('impl') | ||
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| // // In Node.js, EventTarget keeps events behind the kEvents symbol. | ||
| // expect(symbols).toContain('kEvents') | ||
| // }) | ||
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| // test('exposes "Event"', () => { | ||
| // expect(globalThis).toHaveProperty('Event') | ||
| // expect(() => new Event('click')).not.toThrow() | ||
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| // const event = new Event('click') | ||
| // const symbols = Object.getOwnPropertySymbols(event).map( | ||
| // (symbol) => symbol.description, | ||
| // ) | ||
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| // // The "impl" symbol is added by JSDOM. | ||
| // expect(symbols).not.toContain('impl') | ||
| // // Node.js expects events to have the "type" symbol. | ||
| // expect(symbols).toContain('type') | ||
|
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| // /** | ||
| // * Perform a basic "isEvent()" check that Node.js has. | ||
| // * @see https://github.com/nodejs/node/blob/3a456c6db802b5b25594d3a9d235d4989e9f7829/lib/internal/event_target.js#L96 | ||
| // */ | ||
| // expect(event[symbols.find((description) => description === 'type')]).toBe( | ||
| // 'click', | ||
| // ) | ||
| // }) | ||
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| // test('exposes "MessageEvent"', () => { | ||
| // expect(globalThis).toHaveProperty('MessageEvent') | ||
| // expect(() => new MessageEvent('click')).not.toThrow() | ||
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| // const event = new MessageEvent('message') | ||
| // const symbols = Object.getOwnPropertySymbols(event).map( | ||
| // (symbol) => symbol.description, | ||
| // ) | ||
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| // // The "impl" symbol is added by JSDOM. | ||
| // expect(symbols).not.toContain('impl') | ||
| // // Node.js expects events to have the "type" symbol. | ||
| // expect(symbols).toContain('type') | ||
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| // /** | ||
| // * Perform a basic "isEvent()" check that Node.js has. | ||
| // * @see https://github.com/nodejs/node/blob/3a456c6db802b5b25594d3a9d235d4989e9f7829/lib/internal/event_target.js#L96 | ||
| // */ | ||
| // expect(event[symbols.find((description) => description === 'type')]).toBe( | ||
| // 'message', | ||
| // ) | ||
| // }) |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,3 +1,4 @@ | ||
| module.exports = { | ||
| testEnvironment: '<rootDir>/index.js', | ||
| // testEnvironment: '<rootDir>/index.js', | ||
| testEnvironment: 'jsdom', | ||
| } |