test: disable demo project tests

otherwise, node 10 is broken on CI. see jsdom/jsdom#2961 for details.

demo/src/task-scheduler.spec.ts

@@ -1,11 +1,25 @@
 /**
- * @jest-environment jsdom
+ * remove-me @jest-environment jsdom
  */
 /// <reference lib="dom" />
 
 import { MicroTaskScheduler } from './task-scheduler';
 
-describe('task-scheduler', () => {
+/*
+ * We're skipping this test due to JSDOM issue:
+ * https://github.com/jsdom/jsdom/issues/2961
+ *
+ * It should pass on Node >= 12.0, but since the core library
+ * is expected to run on Node >= 10.0, and this test only applies
+ * to the demo project, it's better disabling it for now than
+ * getting false negatives.
+ *
+ * When this test is eventually re-enabled, don't forget to remove
+ * the `remove-me` text at the top of this file to re-enable the
+ * loading of jsdom.
+ */
+// eslint-disable-next-line jest/no-disabled-tests
+describe.skip('task-scheduler', () => {
   let taskScheduler: MicroTaskScheduler;
   let task: jest.Mock;
 

jest.config.js

@@ -1,7 +1,6 @@
 module.exports = {
   preset: 'ts-jest',
   testEnvironment: 'node',
-  setupFiles: ['./jsdom-workaround.js'],
   globals: {
     'ts-jest': {
       tsConfig: 'tsconfig.spec.json',