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Setup

caution

jest-extended only supports Jest version 27.2.5 and newer. If you're using an older version of Jest, use 1.2.1.

Create a setup script with the following:

testSetup.js

// add all jest-extended matchers
import * as matchers from 'jest-extended';
expect.extend(matchers);

// or just add specific matchers
import { toBeArray, toBeSealed } from 'jest-extended';
expect.extend({ toBeArray, toBeSealed });

Add your setup script to your Jest setupFilesAfterEnv configuration. See for help

package.json
"jest": {
  "setupFilesAfterEnv": ["./testSetup.js"]
}

To automatically extend expect with all matchers, you can use

package.json
"jest": {
  "setupFilesAfterEnv": ["jest-extended/all"]
}

Use with vitest​

jest-extended works with vitest because their expect.extend API is compatible. In your setup script:

testSetup.js
import {expect} from "vitest";
import * as matchers from "jest-extended";
expect.extend(matchers);

Add this setup script to your vitest.config.js:

vitest.config.js
export default defineConfig({
  test: {
    setupFiles: ["./testSetup.js"],
  },
});