src: Add proper error handling (#283)

Feature:

    Please see `doc/usage.md` for more information on error-handling.

test/utils.js

@@ -36,6 +36,7 @@ exports = module.exports = {
    * @param  {String} path
    * @param  {Object} [options]
    * @param  {String} [options.method=POST] Method to use
+   * @param  {Object} [options.update] Update object to send.
    * @param  {Object} [options.message] Message to send. Default to a generic text message
    * @param  {Boolean} [options.https=false] Use https
    * @return {Promise}
@@ -47,6 +48,7 @@ exports = module.exports = {
    * @param  {String} token
    * @param  {Object} [options]
    * @param  {String} [options.method=POST] Method to use
+   * @param  {Object} [options.update] Update object to send.
    * @param  {Object} [options.message] Message to send. Default to a generic text message
    * @param  {Boolean} [options.https=false] Use https
    * @return {Promise}
@@ -55,6 +57,9 @@ exports = module.exports = {
   /**
    * Start a mock server at the specified port.
    * @param  {Number} port
+   * @param  {Object} [options]
+   * @param  {Boolean} [options.bad=false] Bad Mock Server; responding with
+   *  unparseable messages
    * @return {Promise}
    */
   startMockServer,
@@ -76,10 +81,13 @@ const statics = require('node-static');
 const servers = {};
 
 
-function startMockServer(port) {
+function startMockServer(port, options = {}) {
   assert.ok(port);
   const server = http.Server((req, res) => {
     servers[port].polling = true;
+    if (options.bad) {
+      return res.end('can not be parsed with JSON.parse()');
+    }
     return res.end(JSON.stringify({
       ok: true,
       result: [{
@@ -153,11 +161,11 @@ function sendWebHookRequest(port, path, options = {}) {
   return request({
     url,
     method: options.method || 'POST',
-    body: {
+    body: options.update || {
       update_id: 1,
       message: options.message || { text: 'test' }
     },
-    json: options.json || true,
+    json: (typeof options.json === 'undefined') ? true : options.json,
   });
 }