Add simple unit test for the background sync service

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

js/tests/service/backgroundsyncservice_spec.js

+/* global expect, Promise, spyOn */
+
+/**
+ * @author Christoph Wurst <christoph@winzerhof-wurst.at>
+ *
+ * Mail
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+define([
+	'radio',
+	'models/account',
+	'models/folder',
+	'service/backgroundsyncservice'
+], function(Radio, Account, Folder, BackgroundSyncService) {
+	describe('Background sync service', function() {
+		it('fails', function(done) {
+			spyOn(Radio.sync, 'request').and.returnValue(Promise.resolve([]));
+			spyOn(Radio.ui, 'trigger');
+			var account = new Account({
+				accountId: -1,
+				isUnified: true
+			});
+			var folder = new Folder({
+				account: account
+			});
+			account.addFolder(folder);
+
+			BackgroundSyncService.sync(account).then(function() {
+				expect(Radio.sync.request).toHaveBeenCalledWith('sync:folder', folder);
+				expect(Radio.ui.trigger).
+					toHaveBeenCalledWith('notification:mail:show', []);
+				done();
+			}).catch(done.fail);
+		});
+	});
+});