diff -r 000000000000 -r 6474c204b198 toolkit/components/thumbnails/test/browser_thumbnails_expiration.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/thumbnails/test/browser_thumbnails_expiration.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,96 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const URL = "http://mochi.test:8888/?t=" + Date.now();
+const URL1 = URL + "#1";
+const URL2 = URL + "#2";
+const URL3 = URL + "#3";
+
+let tmp = {};
+Cc["@mozilla.org/moz/jssubscript-loader;1"]
+  .getService(Ci.mozIJSSubScriptLoader)
+  .loadSubScript("resource://gre/modules/PageThumbs.jsm", tmp);
+
+const {EXPIRATION_MIN_CHUNK_SIZE, PageThumbsExpiration} = tmp;
+
+function runTests() {
+  // Create dummy URLs.
+  let dummyURLs = [];
+  for (let i = 0; i < EXPIRATION_MIN_CHUNK_SIZE + 10; i++) {
+    dummyURLs.push(URL + "#dummy" + i);
+  }
+
+  // Make sure our thumbnails aren't expired too early.
+  dontExpireThumbnailURLs([URL1, URL2, URL3].concat(dummyURLs));
+
+  // Create three thumbnails.
+  yield createDummyThumbnail(URL1);
+  ok(thumbnailExists(URL1), "first thumbnail created");
+
+  yield createDummyThumbnail(URL2);
+  ok(thumbnailExists(URL2), "second thumbnail created");
+
+  yield createDummyThumbnail(URL3);
+  ok(thumbnailExists(URL3), "third thumbnail created");
+
+  // Remove the third thumbnail.
+  yield expireThumbnails([URL1, URL2]);
+  ok(thumbnailExists(URL1), "first thumbnail still exists");
+  ok(thumbnailExists(URL2), "second thumbnail still exists");
+  ok(!thumbnailExists(URL3), "third thumbnail has been removed");
+
+  // Remove the second thumbnail.
+  yield expireThumbnails([URL1]);
+  ok(thumbnailExists(URL1), "first thumbnail still exists");
+  ok(!thumbnailExists(URL2), "second thumbnail has been removed");
+
+  // Remove all thumbnails.
+  yield expireThumbnails([]);
+  ok(!thumbnailExists(URL1), "all thumbnails have been removed");
+
+  // Create some more files than the min chunk size.
+  for (let url of dummyURLs) {
+    yield createDummyThumbnail(url);
+  }
+
+  ok(dummyURLs.every(thumbnailExists), "all dummy thumbnails created");
+
+  // Expire thumbnails and expect 10 remaining.
+  yield expireThumbnails([]);
+  let remainingURLs = [u for (u of dummyURLs) if (thumbnailExists(u))];
+  is(remainingURLs.length, 10, "10 dummy thumbnails remaining");
+
+  // Expire thumbnails again. All should be gone by now.
+  yield expireThumbnails([]);
+  remainingURLs = [u for (u of remainingURLs) if (thumbnailExists(u))];
+  is(remainingURLs.length, 0, "no dummy thumbnails remaining");
+}
+
+function createDummyThumbnail(aURL) {
+  info("Creating dummy thumbnail for " + aURL);
+  let dummy = new Uint8Array(10);
+  for (let i = 0; i < 10; ++i) {
+    dummy[i] = i;
+  }
+  PageThumbsStorage.writeData(aURL, dummy).then(
+    function onSuccess() {
+      info("createDummyThumbnail succeeded");
+      executeSoon(next);
+    },
+    function onFailure(error) {
+      ok(false, "createDummyThumbnail failed " + error);
+    }
+  );
+}
+
+function expireThumbnails(aKeep) {
+  PageThumbsExpiration.expireThumbnails(aKeep).then(
+    function onSuccess() {
+      info("expireThumbnails succeeded");
+      executeSoon(next);
+    },
+    function onFailure(error) {
+      ok(false, "expireThumbnails failed " + error);
+    }
+  );
+}