fix: Prevent mocha tests failures when window does not have focus. (#9332)

* chore: Add puppeteer-core as a dev dependency.

* fix: Make mocha tests run in a fake-focused window.

* fix: Make `test:mocha:interactive` use the same gulp codepath as `test`.

Author: gonfunko

gulpfile.mjs

@@ -45,7 +45,11 @@ import {
   publishBeta,
   recompile,
 } from './scripts/gulpfiles/release_tasks.mjs';
-import {generators, test} from './scripts/gulpfiles/test_tasks.mjs';
+import {
+  generators,
+  interactiveMocha,
+  test,
+} from './scripts/gulpfiles/test_tasks.mjs';
 
 const clean = parallel(cleanBuildDir, cleanReleaseDir);
 
@@ -80,6 +84,7 @@ export {
   clean,
   test,
   generators as testGenerators,
+  interactiveMocha,
   buildAdvancedCompilationTest,
   createRC as gitCreateRC,
   docs,

package-lock.json

@@ -45,7 +45,7 @@
     "test": "gulp test",
     "test:browser": "cd tests/browser && npx mocha",
     "test:generators": "gulp testGenerators",
-    "test:mocha:interactive": "npm run build && concurrently -n tsc,server \"tsc --watch --preserveWatchOutput --outDir \"build/src\" --declarationDir \"build/declarations\"\" \"http-server ./ -o /tests/mocha/index.html -c-1\"",
+    "test:mocha:interactive": "npm run build && concurrently -n tsc,server \"tsc --watch --preserveWatchOutput --outDir \"build/src\" --declarationDir \"build/declarations\"\" \"gulp interactiveMocha\"",
     "test:compile:advanced": "gulp buildAdvancedCompilationTest --debug",
     "updateGithubPages": "npm ci && gulp gitUpdateGithubPages"
   },
@@ -138,6 +138,7 @@
     "patch-package": "^8.0.0",
     "prettier": "^3.3.3",
     "prettier-plugin-organize-imports": "^4.0.0",
+    "puppeteer-core": "^24.17.0",
     "readline-sync": "^1.4.10",
     "rimraf": "^5.0.0",
     "typescript": "^5.3.3",

package.json

@@ -257,9 +257,9 @@ async function metadata() {
  * Run Mocha tests inside a browser.
  * @return {Promise} Asynchronous result.
  */
-async function mocha() {
+async function mocha(exitOnCompletion = true) {
   return runTestTask('mocha', async () => {
-    const result = await runMochaTestsInBrowser().catch(e => {
+    const result = await runMochaTestsInBrowser(exitOnCompletion).catch(e => {
       throw e;
     });
     if (result) {
@@ -269,6 +269,14 @@ async function mocha() {
   });
 }
 
+/**
+ * Run Mocha tests inside a browser and keep the browser open upon completion.
+ * @return {Promise} Asynchronous result.
+ */
+export async function interactiveMocha() {
+  return mocha(false);
+}
+
 /**
  * Helper method for comparison file.
  * @param {string} file1 First target file.

scripts/gulpfiles/test_tasks.mjs

@@ -15,9 +15,12 @@ const {posixPath} = require('../../scripts/helpers');
  * Runs the Mocha tests in this directory in Chrome. It uses webdriverio to
  * launch Chrome and load index.html. Outputs a summary of the test results
  * to the console.
+ *
+ * @param {boolean} exitOnCompletetion True if the browser should automatically
+ *     quit after tests have finished running.
  * @return {number} 0 on success, 1 on failure.
  */
-async function runMochaTestsInBrowser() {
+async function runMochaTestsInBrowser(exitOnCompletion = true) {
   const options = {
     capabilities: {
       browserName: 'chrome',
@@ -45,6 +48,17 @@ async function runMochaTestsInBrowser() {
   console.log('Loading URL: ' + url);
   await browser.url(url);
 
+  // Toggle the devtools setting to emulate focus, so that the window will
+  // always act as if it has focus regardless of the state of the window manager
+  // or operating system. This improves the reliability of FocusManager-related
+  // tests.
+  const puppeteer = await browser.getPuppeteer();
+  await browser.call(async () => {
+    const page = (await puppeteer.pages())[0];
+    const session = await page.createCDPSession();
+    await session.send('Emulation.setFocusEmulationEnabled', { enabled: true });
+  });
+
   await browser.waitUntil(async() => {
     const elem = await browser.$('#failureCount');
     const text = await elem.getAttribute('tests_failed');
@@ -74,7 +88,7 @@ async function runMochaTestsInBrowser() {
   if (parseInt(numOfFailure) !== 0) {
     return 1;
   }
-  await browser.deleteSession();
+  if (exitOnCompletion) await browser.deleteSession();
   return 0;
 }