TextEncoder is not defined before your first test runs — a dependency needs it at import time and jsdom does not have it

Symptom

A component test fails with zero tests run:

● Test suite failed to run
  ReferenceError: TextEncoder is not defined
    > 27 | const enc = new TextEncoder();
    at Object.<anonymous> (../shared/packages/license/src/crypto.ts:27:13)

The stack points into a package you did not touch — a licensing or crypto helper that the component reaches through a context provider. Service tests in the same project (no jsdom, no component) pass.

Cause

• jsdom does not implement the Encoding API, and the Jest jsdom environment does not copy Node's TextEncoder onto the window.
• A constant at module level is evaluated when the module is imported. Imports run before the body of the test file, so a polyfill written in beforeAll — or anywhere below the imports — comes too late. The failure is in the import of the module under test, not in any test.

Fix

A side-effect module that fills the gap from Node, imported as the first line of the test (imports are evaluated in declaration order, so it runs before the dependency is loaded):

// testPolyfills.ts — imported only by tests, never by the bundle
const nodeUtil = require('util') as { TextEncoder?: unknown; TextDecoder?: unknown };
const w = window as unknown as { TextEncoder?: unknown; TextDecoder?: unknown };
if (!w.TextEncoder) w.TextEncoder = nodeUtil.TextEncoder;
if (!w.TextDecoder) w.TextDecoder = nodeUtil.TextDecoder;
export {};

import './testPolyfills';          // FIRST
import * as React from 'react';
import { LicensedPage } from './LicensedPage';

For every suite at once, put the same file into the project's setupFiles. In a Heft project that does not replace the rig's own setupFiles entry: @rushstack/heft-config-file (0.19.x) appends arrays inherited through extends by default, and heft-jest-plugin does not override that for setupFiles (read in the source; we used the first-import route).

The lasting fix belongs in the dependency: create platform objects lazily, inside the function that needs them (function enc() { return new TextEncoder(); }), so importing the module never requires them.

Notes

• The same applies to anything a module touches at import time: crypto.subtle, matchMedia, ResizeObserver.
• After adding a polyfill, assert that it is there (expect(typeof TextEncoder).toBe('function')) — otherwise a later refactor can make the suite green because the code path no longer runs at all.