nodejs + jest : ReferenceError: describe is not defined

Question

The Jest documentation on Globals says the following (emphasis mine).

In your test files, Jest puts each of these methods and objects into the global environment. You don't have to require or import anything to use them. However, if you prefer explicit imports, you can do import {describe, expect, it} from '@jest/globals'.

So, why does typing jest or npm test with scripts.test (in package.json) pointing to jest --verbose cause the ReferenceError: describe is not defined error? Some of the questions around this on SO and elsewhere, mention that, jest should be installed globally, installed with --save-dev, referred to local node_modules, etc. None of them work.

What am I missing?

This is my index.spec.js.

function checkArgs(args) {
  if (args.length > 4) {
    // Error message on extraneous parameters
    return false
  } else if (args.length < 4) {
    // Error message on insufficient parameters
    return false
  } else {
    return true
  }
}

describe("Arguments check", () => {
  test("Number of arguments should be 4", () => {
    expect(checkArgs(process.argv)).toBe(true)
  })
})