[Bug]: Buffer is not instance of UInt8Array in jsdom

[sergekh2]

Version

29.2.2

Steps to reproduce

Clone https://github.com/sergekh2/jest-buffer-test-fail
yarn install
yarn test-node
yarn test-jsdom

Expected behavior

Last test passes.

Actual behavior

Test fails since Buffer is not instance of UInt8Array

Additional context

In node environment node's Buffer is instance of UInt8Array and test passes.

In jsdom Jest brings in Buffer implementation which is not instance of UInt8Array, test fails.

Test code:

test("i-need-buffer", () => {
  const buffer = Buffer.from("hello");
  expect(buffer instanceof Uint8Array).toBe(true);
});

Environment

System:
    OS: macOS 12.6
    CPU: (10) arm64 Apple M1 Max
  Binaries:
    Node: 18.11.0 - ~/.nvm/versions/node/v18.11.0/bin/node
    Yarn: 1.22.18 - /opt/homebrew/bin/yarn
    npm: 8.19.2 - ~/.nvm/versions/node/v18.11.0/bin/npm
  npmPackages:
    jest: ^29.2.2 => 29.2.2

[sergekh2]

I checked previous versions: it succeeds in Jest 25, and fails from 26 onward.

[SimenB]

Buffer shouldn't exist in JSDOM at all - it's a node specific global and will break if you run it in a real browser. I wanna remove it entirely, but there's a performance regression for some reason: #11241.

[sergekh2]

For the browser there are packages like https://www.npmjs.com/package/buffer (which is used by browserify). So it's not a problem at all. The question is how to get consistent experience in JSDOM.

[github-actions]

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