enhance runMochaJSON() helper by returning the subprocess instance

- this allows tests to manually kill a subprocess or interact with it
- also fixed some bad jsdoc

test/integration/helpers.js

@@ -44,17 +44,17 @@ module.exports = {
    * Invokes the mocha binary for the given fixture using the JSON reporter,
    * returning the parsed output, as well as exit code.
    *
-   * @param {string}   fixturePath
-   * @param {array}    args
-   * @param {function} fn
+   * @param {string} fixturePath - Path from __dirname__
+   * @param {string[]} args - Array of args
+   * @param {Function} fn - Callback
    */
   runMochaJSON: function (fixturePath, args, fn) {
     var path;
 
     path = resolveFixturePath(fixturePath);
     args = args || [];
 
-    invokeMocha(args.concat(['--reporter', 'json', path]), function (err, res) {
+    return invokeMocha(args.concat(['--reporter', 'json', path]), function (err, res) {
       if (err) return fn(err);
 
       try {
@@ -134,6 +134,8 @@ function invokeMocha (args, fn) {
       code: code
     });
   });
+
+  return mocha;
 }
 
 function resolveFixturePath (fixture) {