1 files changed, 70 insertions, 0 deletions
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_startup_perf.js b/toolkit/components/extensions/test/xpcshell/test_ext_startup_perf.js
new file mode 100644
index 0000000000..e7108ce100
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_startup_perf.js
@@ -0,0 +1,70 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const STARTUP_APIS = ["backgroundPage"];
+
+const STARTUP_MODULES = new Set([
+  "resource://gre/modules/Extension.sys.mjs",
+  "resource://gre/modules/ExtensionCommon.sys.mjs",
+  "resource://gre/modules/ExtensionParent.sys.mjs",
+  // FIXME: This is only loaded at startup for new extension installs.
+  // Otherwise the data comes from the startup cache. We should test for
+  // this.
+  "resource://gre/modules/ExtensionPermissions.sys.mjs",
+  "resource://gre/modules/ExtensionProcessScript.sys.mjs",
+  "resource://gre/modules/ExtensionUtils.sys.mjs",
+  "resource://gre/modules/ExtensionTelemetry.sys.mjs",
+]);
+
+if (!Services.prefs.getBoolPref("extensions.webextensions.remote")) {
+  STARTUP_MODULES.add("resource://gre/modules/ExtensionChild.sys.mjs");
+  STARTUP_MODULES.add("resource://gre/modules/ExtensionPageChild.sys.mjs");
+}
+
+if (AppConstants.MOZ_APP_NAME == "thunderbird") {
+  // Imported via mail/components/extensions/processScript.js.
+  STARTUP_MODULES.add("resource://gre/modules/ExtensionChild.sys.mjs");
+  STARTUP_MODULES.add("resource://gre/modules/ExtensionContent.sys.mjs");
+  STARTUP_MODULES.add("resource://gre/modules/ExtensionPageChild.sys.mjs");
+}
+
+AddonTestUtils.init(this);
+
+// Tests that only the minimal set of API scripts and modules are loaded at
+// startup for a simple extension.
+add_task(async function test_loaded_scripts() {
+  await ExtensionTestUtils.startAddonManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    background() {},
+    manifest: {},
+  });
+
+  await extension.startup();
+
+  const { apiManager } = ExtensionParent;
+
+  const loadedAPIs = Array.from(apiManager.modules.values())
+    .filter(m => m.loaded || m.asyncLoaded)
+    .map(m => m.namespaceName);
+
+  deepEqual(
+    loadedAPIs.sort(),
+    STARTUP_APIS,
+    "No extra APIs should be loaded at startup for a simple extension"
+  );
+
+  let loadedModules = Cu.loadedJSModules
+    .concat(Cu.loadedESModules)
+    .filter(url => url.startsWith("resource://gre/modules/Extension"));
+
+  deepEqual(
+    loadedModules.sort(),
+    Array.from(STARTUP_MODULES).sort(),
+    "No extra extension modules should be loaded at startup for a simple extension"
+  );
+
+  await extension.unload();
+});