1 files changed, 41 insertions, 0 deletions
diff --git a/browser/base/content/test/general/browser_bug427559.js b/browser/base/content/test/general/browser_bug427559.js
new file mode 100644
index 0000000000..29acf0862b
--- /dev/null
+++ b/browser/base/content/test/general/browser_bug427559.js
@@ -0,0 +1,41 @@
+"use strict";
+
+/*
+ * Test bug 427559 to make sure focused elements that are no longer on the page
+ * will have focus transferred to the window when changing tabs back to that
+ * tab with the now-gone element.
+ */
+
+// Default focus on a button and have it kill itself on blur.
+const URL =
+  "data:text/html;charset=utf-8," +
+  '<body><button onblur="this.remove()">' +
+  "<script>document.body.firstElementChild.focus()</script></body>";
+
+function getFocusedLocalName(browser) {
+  return SpecialPowers.spawn(browser, [], async function () {
+    return content.document.activeElement.localName;
+  });
+}
+
+add_task(async function () {
+  let testTab = await BrowserTestUtils.openNewForegroundTab(gBrowser, URL);
+
+  let browser = testTab.linkedBrowser;
+
+  is(await getFocusedLocalName(browser), "button", "button is focused");
+
+  let blankTab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "about:blank"
+  );
+
+  await BrowserTestUtils.switchTab(gBrowser, testTab);
+
+  // Make sure focus is given to the window because the element is now gone.
+  is(await getFocusedLocalName(browser), "body", "body is focused");
+
+  // Cleanup.
+  gBrowser.removeTab(blankTab);
+  gBrowser.removeCurrentTab();
+});