Babel not transforming custom testEnvironment

[ysfaran]

🐛 Bug Report

With testEnvironment configuration option a custom test environment can be specified. Babel seems to skip the specified testEnvironment file and only transforms test files. This causes confusion since test code is transformed differently from the testEnvironment file.

To Reproduce

Steps to reproduce the behavior:

babel.config.js

module.exports = {
  presets: [["@babel/preset-env", { targets: { node: "current" } }]],
};

jest.config.js

module.exports = {
  rootDir: ".",
  testEnvironment: "<rootDir>/custom-environment.js",
};

custom-environment.js

const NodeEnvironment = require("jest-environment-node");

const test = {};
console.log("environment: " + test.a?.b);

class NodeEnvironmentFailFast extends NodeEnvironment {}

module.exports = NodeEnvironmentFailFast;

optional-chaining.spec.js

it("check optional chaining", () => {
  const test = {};
  console.log("test: " + test.a?.b);
});

package.json

{
  "name": "GoodPracticalProgrammingmacro",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "jest": "^26.6.3",
    "jest-environment-node": "^26.6.2",
    "@babel/preset-env": "7.12.11"
  }
}

Executing above test in a Node 12 environment (which doesn't support optional chaining) will fail with following output:

> jest
 FAIL  ./optional-chaining.test.js
  ● Test suite failed to run

    /home/runner/jest-playground/custom-environment.js:4
    console.log("environment: " + test.a?.b);
                                         ^

    SyntaxError: Unexpected token '.'

      at node_modules/jest-runner/build/runTest.js:259:7

Test Suites: 1 failed, 1 total
Tests:       0 total
Snapshots:   0 total
Time:        0.077s, estimated 12s
Ran all test suites.
exit status 1

If you comment the line mentioned in the error output (console.log("environment: " + test.a?.b);) it will work just fine, which indicates that optional-chaining.test.js is transformed properly, while custom-environment.js isn't.

Expected behavior

Babel should also transform testEnvironment file (in this case custom-environment.js) just as any other file.

Link to repl or repo

https://repl.it/join/kbuocjuy-ysfaran

envinfo

root@bacf2e4aeae1:/app# npx envinfo --preset jest
npx: installed 1 in 0.912s

  System:
    OS: Linux 4.19 Debian GNU/Linux 9 (stretch) 9 (stretch)
    CPU: (6) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
  Binaries:
    Node: 12.20.1 - /usr/local/bin/node
    Yarn: 1.22.5 - /usr/local/bin/yarn
    npm: 6.14.10 - /usr/local/bin/npm
  npmPackages:
    jest: ^26.6.3 => 26.6.3

[ahnpnl]

This has been done in #8751 under next tag

[github-actions]

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