diff -r 000000000000 -r 6474c204b198 browser/components/tabview/test/browser_tabview_bug631752.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/tabview/test/browser_tabview_bug631752.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,85 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function test() {
+  let cw;
+  let groupItem;
+
+  let getTabItemAspect = function (tabItem) {
+    let bounds = cw.iQ('.thumb', tabItem.container).bounds();
+    let padding = cw.TabItems.tabItemPadding;
+    return (bounds.height + padding.y) / (bounds.width + padding.x);
+  }
+
+  let getAspectRange = function () {
+    let aspect = cw.TabItems.tabAspect;
+    let variance = aspect / 100 * 1.5;
+    return new cw.Range(aspect - variance, aspect + variance);
+  }
+
+  let dragTabItem = function (tabItem) {
+    let doc = cw.document.documentElement;
+    let tabItem = groupItem.getChild(0);
+    let container = tabItem.container;
+    let aspectRange = getAspectRange();
+
+    EventUtils.synthesizeMouseAtCenter(container, {type: "mousedown"}, cw);
+    for (let x = 200; x <= 400; x += 100)
+      EventUtils.synthesizeMouse(doc, x, 100, {type: "mousemove"}, cw);
+    ok(aspectRange.contains(getTabItemAspect(tabItem)), "tabItem's aspect is correct");
+
+    ok(!groupItem.getBounds().intersects(tabItem.getBounds()), "tabItem was moved out of group bounds");
+    ok(!tabItem.parent, "tabItem is orphaned");
+
+    EventUtils.synthesizeMouseAtCenter(container, {type: "mouseup"}, cw);
+    ok(aspectRange.contains(getTabItemAspect(tabItem)), "tabItem's aspect is correct");
+  }
+
+  let testDragOutOfStackedGroup = function () {
+    dragTabItem();
+
+    let secondGroup = cw.GroupItems.groupItems[1];
+    closeGroupItem(secondGroup, testDragOutOfExpandedStackedGroup);
+  }
+
+  let testDragOutOfExpandedStackedGroup = function () {
+    groupItem.addSubscriber("expanded", function onExpanded() {
+      groupItem.removeSubscriber("expanded", onExpanded);
+      dragTabItem();
+    });
+
+    groupItem.addSubscriber("collapsed", function onCollapsed() {
+      groupItem.removeSubscriber("collapsed", onCollapsed);
+
+      let secondGroup = cw.GroupItems.groupItems[1];
+      closeGroupItem(secondGroup, function () hideTabView(finishTest));
+    });
+
+    groupItem.expand();
+  }
+
+  let finishTest = function () {
+    is(cw.GroupItems.groupItems.length, 1, "there is one groupItem");
+    is(gBrowser.tabs.length, 1, "there is one tab");
+    ok(!TabView.isVisible(), "tabview is hidden");
+
+    finish();
+  }
+
+  waitForExplicitFinish();
+
+  newWindowWithTabView(function (win) {
+    registerCleanupFunction(function () win.close());
+
+    cw = win.TabView.getContentWindow();
+
+    groupItem = cw.GroupItems.groupItems[0];
+    groupItem.setSize(200, 200, true);
+
+    for (let i = 0; i < 9; i++)
+      win.gBrowser.addTab();
+
+    ok(groupItem.isStacked(), "groupItem is stacked");
+    testDragOutOfStackedGroup();
+  });
+}