diff -r 000000000000 -r 6474c204b198 browser/base/content/test/newtab/browser_newtab_update.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/base/content/test/newtab/browser_newtab_update.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,53 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Checks that newtab is updated as its links change.
+ */
+
+function runTests() {
+  if (NewTabUtils.allPages.updateScheduledForHiddenPages) {
+    // Wait for dynamic updates triggered by the previous test to finish.
+    yield whenPagesUpdated(null, true);
+  }
+
+  // First, start with an empty page.  setLinks will trigger a hidden page
+  // update because it calls clearHistory.  We need to wait for that update to
+  // happen so that the next time we wait for a page update below, we catch the
+  // right update and not the one triggered by setLinks.
+  //
+  // Why this weird way of yielding?  First, these two functions don't return
+  // promises, they call TestRunner.next when done.  Second, the point at which
+  // setLinks is done is independent of when the page update will happen, so
+  // calling whenPagesUpdated cannot wait until that time.
+  setLinks([]);
+  whenPagesUpdated(null, true);
+  yield null;
+  yield null;
+
+  // Strategy: Add some visits, open a new page, check the grid, repeat.
+  fillHistory([link(1)]);
+  yield whenPagesUpdated(null, true);
+  yield addNewTabPageTab();
+  checkGrid("1,,,,,,,,");
+
+  fillHistory([link(2)]);
+  yield whenPagesUpdated(null, true);
+  yield addNewTabPageTab();
+  checkGrid("2,1,,,,,,,");
+
+  fillHistory([link(1)]);
+  yield whenPagesUpdated(null, true);
+  yield addNewTabPageTab();
+  checkGrid("1,2,,,,,,,");
+
+  // Wait for fillHistory to add all links before waiting for an update
+  yield fillHistory([link(2), link(3), link(4)], TestRunner.next);
+  yield whenPagesUpdated(null, true);
+  yield addNewTabPageTab();
+  checkGrid("2,1,3,4,,,,,");
+}
+
+function link(id) {
+  return { url: "http://example.com/#" + id, title: "site#" + id };
+}