diff --git a/tests/bootstrap.js b/tests/bootstrap.js
index 0310b32bf..32003eecf 100644
--- a/tests/bootstrap.js
+++ b/tests/bootstrap.js
@@ -39,12 +39,14 @@
   const isIe = navigator.userAgent.indexOf('MSIE') !== -1 ||
       navigator.appVersion.indexOf('Trident/') > -1;
   const localhosts = ['localhost', '127.0.0.1', '[::1]'];
+  const isLocalhost = localhosts.includes(location.hostname);
+  const isFileUrl = location.origin === 'file://';
 
   // Default bootstrap options.
   const options = {
     // Decide whether to use compmiled mode or not.  Please see issue
     // #5557 for more information.
-    loadCompressed: isIe || !localhosts.includes(location.hostname),
+    loadCompressed: isIe || !(isLocalhost || isFileUrl),
 
     // URL of the blockly repository.  This is needed for a few reasons:
     //
diff --git a/tests/generators/index.html b/tests/generators/index.html
index 9e37f05b6..49a9d5f9d 100644
--- a/tests/generators/index.html
+++ b/tests/generators/index.html
@@ -3,41 +3,36 @@
 <head>
 <meta charset="utf-8">
 <title>Blockly Generator Tests</title>
-<script src="../../blockly_uncompressed.js"></script>
-<script src="../../msg/messages.js"></script>
-
 <script>
-// Require optional modules needed by tests.
-goog.require('Blockly.Dart.all');
-goog.require('Blockly.JavaScript.all');
-goog.require('Blockly.Lua.all');
-goog.require('Blockly.PHP.all');
-goog.require('Blockly.Python.all');
-goog.require('Blockly.libraryBlocks');
+  var BLOCKLY_BOOTSTRAP_OPTIONS = {
+    additionalScripts: [
+      'msg/messages.js',
+      'tests/generators/unittest_javascript.js',
+      'tests/generators/unittest_python.js',
+      'tests/generators/unittest_php.js',
+      'tests/generators/unittest_lua.js',
+      'tests/generators/unittest_dart.js',
+      'tests/generators/unittest.js',
+    ],
+  }
 </script>
-<script src="unittest_javascript.js"></script>
-<script src="unittest_python.js"></script>
-<script src="unittest_php.js"></script>
-<script src="unittest_lua.js"></script>
-<script src="unittest_dart.js"></script>
-<script src="unittest.js"></script>
+<script src="../bootstrap.js"></script>
 <script>
-'use strict';
-
 var demoWorkspace = null;
 var outputCode = '';
 
 function start() {
-  demoWorkspace = Blockly.inject('blocklyDiv',
-      {grid:
-         {spacing: 25,
-          length: 3,
-          colour: '#ccc',
-          snap: true},
-       media: '../../media/',
-       toolbox: document.getElementById('toolbox'),
-       zoom: {controls: true, wheel: true}
-       });
+  demoWorkspace = Blockly.inject('blocklyDiv', {
+    grid: {
+      spacing: 25,
+      length: 3,
+      colour: '#ccc',
+      snap: true
+    },
+    media: '../../media/',
+    toolbox: document.getElementById('toolbox'),
+    zoom: {controls: true, wheel: true}
+  });
   changeIndex();
 }
 
@@ -210,6 +205,11 @@ function changeIndex() {
   demoWorkspace.getToolbox().flyout_.workspace_.options.oneBasedIndex = oneBasedIndex;
 }
 </script>
+<script type=module>
+// Wait for Blockly to finish loading.
+import Blockly from "../blockly.mjs";
+start();
+</script>
 
 <style>
 html, body {
@@ -240,7 +240,7 @@ h1 {
 }
 </style>
 </head>
-<body onload="start()">
+<body>
 
   <div id="blocklyDiv"></div>
 
