1 files changed, 28 insertions, 0 deletions
diff --git a/browser/base/content/test/tabs/browser_tabswitch_updatecommands.js b/browser/base/content/test/tabs/browser_tabswitch_updatecommands.js
new file mode 100644
index 0000000000..b5d2762eec
--- /dev/null
+++ b/browser/base/content/test/tabs/browser_tabswitch_updatecommands.js
@@ -0,0 +1,28 @@
+// This test ensures that only one command update happens when switching tabs.
+
+"use strict";
+
+add_task(async function () {
+  const uri = "data:text/html,<body><input>";
+  let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, uri);
+  let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, uri);
+
+  let updates = [];
+  function countUpdates(event) {
+    updates.push(new Error().stack);
+  }
+  let updater = document.getElementById("editMenuCommandSetAll");
+  updater.addEventListener("commandupdate", countUpdates, true);
+  await BrowserTestUtils.switchTab(gBrowser, tab1);
+
+  is(updates.length, 1, "only one command update per tab switch");
+  if (updates.length > 1) {
+    for (let stack of updates) {
+      info("Update stack:\n" + stack);
+    }
+  }
+
+  updater.removeEventListener("commandupdate", countUpdates, true);
+  BrowserTestUtils.removeTab(tab1);
+  BrowserTestUtils.removeTab(tab2);
+});