Minimal repro for Jest 26 -> 29 upgrade issue

This example demonstrates an error that appears in tests as a result of upgrading Jest from v26 to v29 in a Next.js 12 application. The issue relates to dependencies that are shipped as ES modules. For this example, I've used the Nano ID package but any ESM package should do.

The test file is as follows:

import getId from './index';

describe('simple test', () => {
  it('should work', () => {
    const id = getId();
    expect(id).toBeDefined();
  });
});

The file under test (index.js) contains this code:

import { customAlphabet } from 'nanoid';

export default customAlphabet('0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz', 10);

The git repo has two branches:

• jest-26
• main (where jest 29 is used)

The only difference between the branches is the Jest version used.

Jest 26

Running the following commands

> git switch jest-26
> npm i
> npm test

yields the following output

(node:40424) ExperimentalWarning: VM Modules is an experimental feature. This feature could change at any time
(Use `node --trace-warnings ...` to show where the warning was created)
 PASS  src/index.test.js
  simple test
    ✓ should work (1 ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        0.656 s
Ran all test suites.

Jest 29

Running the following commands

> git switch main
> npm i
> npm test

yields the following output

 FAIL  src/index.test.js
  ● Test suite failed to run

    Must use import to load ES Module: /Users/eirikur/Projects/jest-esm-issue-repro/node_modules/nanoid/index.browser.js

    > 1 | import { customAlphabet } from 'nanoid';
        | ^
      2 |
      3 | export default customAlphabet('0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz', 10);
      4 |

      at Runtime.requireModule (node_modules/jest-runtime/build/index.js:817:21)
      at Object.<anonymous> (src/index.js:1:1)
      at Object.<anonymous> (src/index.test.js:1:1)

Test Suites: 1 failed, 1 total
Tests:       0 total
Snapshots:   0 total
Time:        0.509 s
Ran all test suites.

Node/NPM version

npm:  8.18.0
node: v16.16.0