1 files changed, 62 insertions, 0 deletions
diff --git a/browser/base/content/test/tabs/browser_tabReorder_overflow.js b/browser/base/content/test/tabs/browser_tabReorder_overflow.js
new file mode 100644
index 0000000000..a74677204f
--- /dev/null
+++ b/browser/base/content/test/tabs/browser_tabReorder_overflow.js
@@ -0,0 +1,62 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+requestLongerTimeout(2);
+
+add_task(async function () {
+  let initialTabsLength = gBrowser.tabs.length;
+
+  let arrowScrollbox = gBrowser.tabContainer.arrowScrollbox;
+  let tabMinWidth = parseInt(
+    getComputedStyle(gBrowser.selectedTab, null).minWidth
+  );
+
+  let width = ele => ele.getBoundingClientRect().width;
+
+  let tabCountForOverflow = Math.ceil(
+    (width(arrowScrollbox) / tabMinWidth) * 1.1
+  );
+
+  let newTab1 = (gBrowser.selectedTab = BrowserTestUtils.addTab(
+    gBrowser,
+    "about:robots",
+    { skipAnimation: true }
+  ));
+  let newTab2 = (gBrowser.selectedTab = BrowserTestUtils.addTab(
+    gBrowser,
+    "about:about",
+    { skipAnimation: true }
+  ));
+  let newTab3 = (gBrowser.selectedTab = BrowserTestUtils.addTab(
+    gBrowser,
+    "about:config",
+    { skipAnimation: true }
+  ));
+
+  await BrowserTestUtils.overflowTabs(registerCleanupFunction, window, {
+    overflowAtStart: false,
+  });
+
+  registerCleanupFunction(function () {
+    while (gBrowser.tabs.length > initialTabsLength) {
+      gBrowser.removeTab(
+        gBrowser.tabContainer.getItemAtIndex(initialTabsLength)
+      );
+    }
+  });
+
+  let tabs = gBrowser.tabs;
+  is(tabs.length, tabCountForOverflow, "new tabs are opened");
+  is(tabs[initialTabsLength], newTab1, "newTab1 position is correct");
+  is(tabs[initialTabsLength + 1], newTab2, "newTab2 position is correct");
+  is(tabs[initialTabsLength + 2], newTab3, "newTab3 position is correct");
+
+  await dragAndDrop(newTab1, newTab2, false);
+  tabs = gBrowser.tabs;
+  is(tabs.length, tabCountForOverflow, "tabs are still there");
+  is(tabs[initialTabsLength], newTab2, "newTab2 and newTab1 are swapped");
+  is(tabs[initialTabsLength + 1], newTab1, "newTab1 and newTab2 are swapped");
+  is(tabs[initialTabsLength + 2], newTab3, "newTab3 stays same place");
+});