1 files changed, 37 insertions, 0 deletions
diff --git a/browser/components/customizableui/test/browser_currentset_post_reset.js b/browser/components/customizableui/test/browser_currentset_post_reset.js
new file mode 100644
index 0000000000..31bcd150b1
--- /dev/null
+++ b/browser/components/customizableui/test/browser_currentset_post_reset.js
@@ -0,0 +1,37 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+function checkSpacers() {
+  let navbarWidgets = CustomizableUI.getWidgetIdsInArea("nav-bar");
+  let currentSetWidgets = CustomizableUI.getTestOnlyInternalProp(
+    "CustomizableUIInternal"
+  )._getCurrentWidgetsInContainer(document.getElementById("nav-bar"));
+  navbarWidgets = navbarWidgets.filter(w => CustomizableUI.isSpecialWidget(w));
+  currentSetWidgets = currentSetWidgets.filter(w =>
+    CustomizableUI.isSpecialWidget(w)
+  );
+  Assert.deepEqual(
+    navbarWidgets,
+    currentSetWidgets,
+    "Should have the same 'special' widgets in currentset and placements"
+  );
+}
+
+/**
+ * Check that after a reset, CUI's internal bookkeeping correctly deals with flexible spacers.
+ */
+add_task(async function () {
+  await startCustomizing();
+  checkSpacers();
+
+  CustomizableUI.addWidgetToArea(
+    "spring",
+    "nav-bar",
+    4 /* Insert before the last extant spacer */
+  );
+  await gCustomizeMode.reset();
+  checkSpacers();
+  await endCustomizing();
+});