Add test for TileUtils.

tests/lib/TileUtils.test.js

@@ -0,0 +1,21 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+/* jshint node:true, esnext:true */
+
+const TileUtils = require("lib/TileUtils");
+const assert = require("chai").assert;
+
+describe("TileUtils", function() {
+  "use strict";
+
+  var firstLink = {url: "http://example0.com/", title: "site#0", frecency: 1, lastVisitDate: 1};
+  var secondLink = {url: "http://example1.com/", title: "site#1", frecency: 3, lastVisitDate: 1};
+  var thirdLink = {url: "http://example2.com/", title: "site#2", frecency: 3, lastVisitDate: 1};
+
+  it("should merge links", () => {
+    var merged = JSON.stringify(TileUtils.getMergedLinks([[firstLink, thirdLink], [secondLink]]));
+    assert.equal(merged, JSON.stringify([secondLink, thirdLink, firstLink]));
+  });
+
+});