test: Refactor mocha test infrastructure

packages/blockly/gulpfile.mjs

@@ -37,11 +37,7 @@ import {
   pack,
   typings,
 } from './scripts/gulpfiles/package_tasks.mjs';
-import {
-  generators,
-  interactiveMocha,
-  test,
-} from './scripts/gulpfiles/test_tasks.mjs';
+import {generators, test} from './scripts/gulpfiles/test_tasks.mjs';
 
 const clean = parallel(cleanBuildDir, cleanReleaseDir);
 
@@ -73,7 +69,6 @@ export {
   clean,
   test,
   generators as testGenerators,
-  interactiveMocha,
   buildAdvancedCompilationTest,
   docs,
   typings,

packages/blockly/package.json

@@ -21,6 +21,7 @@
   },
   "imports": {
     "#core/*": "./build/src/core/*",
+    "#blocks/*": "./build/src/blocks/*",
     "#generators/*": "./build/src/generators/*"
   },
   "publishConfig": {
@@ -80,7 +81,7 @@
     "test:browser": "npx mocha --config tests/browser/.mocharc.js",
     "test:mocha:node": "npx mocha --config tests/mocha/.mocharc.node.cjs \"tests/mocha/**/*_test.js\"",
     "test:generators": "gulp testGenerators",
-    "test:mocha:interactive": "npm run build && concurrently -n tsc,server \"tsc --watch --preserveWatchOutput --outDir \"build/src\" --declarationDir \"build/declarations\"\" \"gulp interactiveMocha\"",
+    "test:mocha:interactive": "npm run build && node scripts/prepare_mocha_bundle.mjs && concurrently -n tsc,esbuild,python3 \"tsc --watch --preserveWatchOutput --outDir \"build/src\" --declarationDir \"build/declarations\"\" \"esbuild build/tests/bundle-entry.js --bundle --sourcemap --alias:blockly/core=./build/src/core/blockly.js --alias:blockly/blocks=./build/src/blocks/blocks.js --alias:blockly=./build/src/core/blockly.js --outfile=build/tests/mocha-bundle.js --servedir=. --serve=127.0.0.1:8080 --watch=forever --log-level=warning\" \"python3 -m webbrowser 'http://localhost:8080/tests/mocha/index.html'\"",
     "test:compile:advanced": "gulp buildAdvancedCompilationTest --debug",
     "updateGithubPages": "npm ci && node scripts/update_github_pages.mjs --upstream",
     "updateGithubPages:staging": "npm ci && node scripts/update_github_pages.mjs --use-local"
@@ -144,11 +145,11 @@
     "async-done": "^2.0.0",
     "chai": "^6.2.2",
     "concurrently": "^10.0.4",
+    "esbuild": "^0.28.2",
     "glob": "^13.0.6",
-    "google-closure-compiler": "^20260803.0.0",
+    "google-closure-compiler": "^20260819.0.0",
     "gulp": "^5.0.1",
     "gulp-concat": "^2.6.1",
-    "gulp-gzip": "^1.4.2",
     "gulp-rename": "^2.1.0",
     "gulp-replace": "^1.1.4",
     "gulp-sourcemaps": "^3.0.0",

packages/blockly/scripts/gulpfiles/test_tasks.mjs

@@ -12,15 +12,11 @@
 import asyncDone from 'async-done';
 import {spawnSync} from 'child_process';
 import * as fs from 'fs';
-import {globSync} from 'glob';
 import * as gulp from 'gulp';
-import gzip from 'gulp-gzip';
 import * as path from 'path';
 import {rimraf} from 'rimraf';
 
-import {RELEASE_DIR, TEST_TSC_OUTPUT_DIR} from './config.mjs';
-
-import {runMochaTestsInBrowser} from '../../tests/mocha/webdriver.js';
+import {TEST_TSC_OUTPUT_DIR} from './config.mjs';
 
 const OUTPUT_DIR = 'build/generators';
 const GOLDEN_DIR = 'tests/generators/golden';
@@ -168,146 +164,13 @@ function renamings() {
 }
 
 /**
- * Helper method for gzipping file.
- * @param {string} file Target file.
- * @return {Promise} Asynchronous result.
- */
-function gzipFile(file) {
-  return new Promise((resolve) => {
-    const name = path.posix.join(RELEASE_DIR, file);
-
-    const stream = gulp.src(name)
-        .pipe(gzip())
-        .pipe(gulp.dest(RELEASE_DIR));
-
-    stream.on('end', () => {
-      resolve();
-    });
-  });
-}
-
-/**
- * Helper method for comparing file size.
- * @param {string} file Target file.
- * @param {number} expected Expected size.
- * @return {number} 0: success / 1: failed.
- */
-function compareSize(file, expected) {
-  const name = path.posix.join(RELEASE_DIR, file);
-  const compare = Math.floor(expected * 1.1);
-  const stat = fs.statSync(name);
-  const size = stat.size;
-
-  if (!compare) {
-    const message = `Failed: Previous size of ${name} is undefined.`;
-    console.log(`${BOLD_RED}${message}${ANSI_RESET}`);
-    return 1;
-  }
-
-  if (size > compare) {
-    const message = `Failed: ` +
-        `Size of ${name} has grown more than 10%. ${size} vs ${expected}`;
-    console.log(`${BOLD_RED}${message}${ANSI_RESET}`);
-    return 1;
-  }
-
-  const message =
-      `Size of ${name} at ${size} compared to previous ${expected}`;
-  console.log(`${BOLD_GREEN}${message}${ANSI_RESET}`);
-  return 0;
-}
-
-/**
- * Helper method for zipping the compressed files.
- * @return {Promise} Asynchronous result.
- */
-function zippingFiles() {
-  // GZip them for additional size comparisons (keep originals, force
-  // overwite previously-gzipped copies).
-  console.log('Zipping the compressed files');
-  const gzip1 = gzipFile('blockly_compressed.js');
-  const gzip2 = gzipFile('blocks_compressed.js');
-  return Promise.all([gzip1, gzip2]);
-}
-
-/**
- * Check the sizes of built files for unexpected growth.
- * @return {Promise} Asynchronous result.
- */
-async function metadata() {
-  return runTestTask('metadata', async () => {
-    // Zipping the compressed files.
-    await zippingFiles();
-    // Read expected size from script.
-    const contents = fs.readFileSync('tests/scripts/check_metadata.sh')
-        .toString();
-    const pattern = /^readonly (?<key>[A-Z_]+)=(?<value>\d+)$/gm;
-    const matches = contents.matchAll(pattern);
-    const expected = {};
-    for (const match of matches) {
-      expected[match.groups.key] = match.groups.value;
-    }
-
-    // Check the sizes of the files.
-    let failed = 0;
-    failed += compareSize('blockly_compressed.js',
-                          expected.BLOCKLY_SIZE_EXPECTED);
-    failed += compareSize('blocks_compressed.js',
-                          expected.BLOCKS_SIZE_EXPECTED);
-    failed += compareSize('blockly_compressed.js.gz',
-                          expected.BLOCKLY_GZ_SIZE_EXPECTED);
-    failed += compareSize('blocks_compressed.js.gz',
-                          expected.BLOCKS_GZ_SIZE_EXPECTED);
-    if (failed > 0) {
-      throw new Error('Unexpected growth was detected.');
-    }
-  });
-}
-
-/**
- * Generates tests/mocha/test-modules.generated.mjs,
- * the list of tests imported by the browser harness (tests/mocha/index.html).
- * Keeping it generated from a glob means new *_test.js files are picked up
- * automatically and the browser and Node runners stay in sync.
- * @return {Promise} Asynchronous result.
- */
-function generateMochaIndex() {
-  return runTestTask('generateMochaIndex', async () => {
-    const files = globSync('**/*_test.js', {cwd: 'tests/mocha'}).sort();
-
-    const body = files.map((f) => `import './${f}';`).join('\n') + '\n';
-    fs.writeFileSync('tests/mocha/test-modules.generated.mjs', body);
-  });
-}
-
-/**
- * Run Mocha tests inside a browser.
+ * Run Mocha tests under Node.
  * @return {Promise} Asynchronous result.
  */
 function mocha() {
-  // Run in a subprocess so webdriverio is not loaded inside gulp's asyncDone
-  // domain (which has been observed to exit the process on CI after ~2s).
-  return runTestCommand('mocha', 'node tests/mocha/webdriver.js');
+  return runTestCommand('mocha', 'npm run test:mocha:node');
 }
 
-/**
- * Run Mocha tests inside a browser and keep the browser open upon completion.
- * @return {Promise} Asynchronous result.
- */
-export const interactiveMocha = gulp.series(
-  generateMochaIndex,
-  function interactiveMochaRun() {
-    return runTestTask('interactiveMocha', () => {
-      return runMochaTestsInBrowser(false).then((result) => {
-        if (result) {
-          throw new Error('Mocha tests failed');
-        }
-        console.log('Mocha tests passed');
-      });
-    });
-  },
-);
-
 /**
  * Helper method for comparison file.
  * @param {string} file1 First target file.
@@ -429,7 +292,6 @@ const tasks = [
   // Build must run before the remaining tasks
   build,
   renamings,
-  generateMochaIndex,
   mocha,
   generators,
   typeDefinitions,

packages/blockly/scripts/prepare_mocha_bundle.mjs

@@ -0,0 +1,43 @@
+/**
+ * @license
+ * Copyright 2026 Raspberry Pi Foundation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {globSync} from 'glob';
+import * as fs from 'node:fs/promises';
+import {createRequire} from 'node:module';
+import * as path from 'node:path';
+
+const require = createRequire(import.meta.url);
+
+const TEST_DIR = 'tests/mocha';
+const OUT_DIR = 'build/tests';
+const ENTRY_POINT = path.posix.join(OUT_DIR, 'bundle-entry.js');
+
+/**
+ * Writes out a file that loads the in-browser Mocha test bootstrap code and
+ * the tests themselves, and acts as an entrypoint for esbuild to enumerate and
+ * bundle the various scripts that make up the test suite.
+ */
+async function writeEntryPoint() {
+  const tests = globSync('**/*_test.{js,ts}', {cwd: TEST_DIR}).sort();
+  const dir = path.posix.relative(path.posix.dirname(ENTRY_POINT), TEST_DIR);
+
+  await fs.writeFile(
+    ENTRY_POINT,
+    [
+      `import '${dir}/browser-setup.js';`,
+      ...tests.map((file) => `import '${dir}/${file}';`),
+    ].join('\n'),
+  );
+}
+
+await fs.mkdir(OUT_DIR, {recursive: true});
+// Resolve and copy Mocha's prebuilt browser distribution.
+await fs.copyFile(
+  require.resolve('mocha/mocha.js'),
+  path.join(OUT_DIR, 'mocha.js'),
+);
+// Write out the esbuild entrypoint that imports the test files.
+await writeEntryPoint();

packages/blockly/tests/mocha/.mocharc.node.cjs

@@ -14,7 +14,8 @@
 
 module.exports = {
   ui: 'tdd',
-  reporter: 'spec',
+  'node-option': ['enable-source-maps'],
+  reporter: './tests/mocha/quiet_reporter.cjs',
   parallel: true,
   require: ['./tests/mocha/node-setup.mjs'],
   timeout: 10000,

packages/blockly/tests/mocha/browser-setup.js

@@ -0,0 +1,40 @@
+/**
+ * @license
+ * Copyright 2026 Raspberry Pi Foundation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Browser harness for the Blockly unit suite.
+ *
+ * This is the browser counterpart to node-setup.mjs: it loads Blockly, exposes
+ * the globals the tests expect, installs the shared DOM fixtures and configures
+ * Mocha. It is bundled, along with every test module, into
+ * build/tests/mocha-bundle.js, which is loaded by the test page.
+ */
+
+// Prevent Prettier from reordering imports to load blocks before Blockly.
+// organize-imports-ignore
+import * as Blockly from '#core/blockly.js';
+import '#blocks/blocks.js';
+import {javascriptGenerator} from '#generators/javascript.js';
+import {config as chaiConfig} from 'chai';
+import sinon from 'sinon';
+import 'mocha/mocha.css';
+import {installFixtures} from './test_helpers/dom_fixtures.js';
+import '@blockly/block-test';
+
+chaiConfig.showDiff = false;
+
+globalThis.Blockly = Blockly;
+globalThis.javascriptGenerator = javascriptGenerator;
+globalThis.sinon = sinon;
+
+// The focusable trees, toolbox definitions and #blocklyDiv the tests expect.
+// Shared with the Node harness so both run against identical markup.
+installFixtures();
+
+mocha.setup({
+  ui: 'tdd',
+  failZero: true,
+});

packages/blockly/tests/mocha/dropdowndiv_test.js

@@ -177,10 +177,8 @@ suite('DropDownDiv', function () {
       const block = this.setUpBlockWithField();
       const field = Array.from(block.getFields())[0];
 
-      const errorMsgRegex = /Cannot read properties of null.+?/;
-      assert.throws(
-        () => Blockly.DropDownDiv.show(field, false, 50, 60, 70, 80, false),
-        errorMsgRegex,
+      assert.throws(() =>
+        Blockly.DropDownDiv.show(field, false, 50, 60, 70, 80, false),
       );
     });