internal: Ensure jsdom test env has modern globals

Author: ntucker

docs/core/guides/unit-testing-hooks.md

@@ -38,7 +38,7 @@ to `renderDataHook()` will result in a completely fresh cache state as well as m
 
 :::
 
-### Polyfill fetch in node
+### Polyfill fetch in node < 18
 
 Node doesn't come with fetch out of the box, so we need to be sure to polyfill it.
 

scripts/testSetup.js

@@ -3,3 +3,24 @@ require('core-js/stable');
 window.requestIdleCallback = jest.fn().mockImplementation(cb => {
   cb();
 });
+if (!globalThis.TextEncoder || !globalThis.TextDecoder) {
+  const { TextDecoder, TextEncoder } = require('node:util');
+  globalThis.TextEncoder = TextEncoder;
+  globalThis.TextDecoder = TextDecoder;
+}
+
+if (!globalThis.ReadableStream || !globalThis.WritableStream) {
+  const { ReadableStream, WritableStream } = require('node:stream/web');
+  globalThis.ReadableStream = ReadableStream;
+  globalThis.WritableStream = WritableStream;
+}
+
+if (!globalThis.TextEncoderStream) {
+  const { TextEncoderStream } = require('node:stream/web');
+  globalThis.TextEncoderStream = TextEncoderStream;
+}
+
+if (!globalThis.TransformStream) {
+  const { TransformStream } = require('node:stream/web');
+  globalThis.TransformStream = TransformStream;
+}