Make chromedriver.start return a promise that resolves once chromedriver is ready

README.md

@@ -143,6 +143,18 @@ chromedriver.start(args);
 chromedriver.stop();
 
 ```
+
+With the latest version, you can optionally receive a Promise from the `chromedriver.start` function:
+
+```javascript
+var returnPromise = true;
+chromedriver
+  .start(args, returnPromise)
+  .then(() => {
+    console.log('chromedriver is ready');
+  });
+```
+
 Note: if your tests are ran asynchronously, chromedriver.stop() will have to be
 executed as a callback at the end of your tests
 

lib/chromedriver.js

@@ -1,13 +1,37 @@
 var path = require('path');
+var tcpPortUsed = require('tcp-port-used');
+function getPortFromArgs(args) {
+  var port = 9515;
+  if (!args){
+    return port;
+  }
+  var portRegexp = /--port=(\d*)/;
+  var portArg = args.find(function (arg) {
+    return portRegexp.test(arg);
+  });
+  if (portArg){
+    port = parseInt(portRegexp.exec(portArg)[1]);
+  }
+  return port;
+};
 process.env.PATH = path.join(__dirname, 'chromedriver') + path.delimiter + process.env.PATH;
 exports.path = process.platform === 'win32' ? path.join(__dirname, 'chromedriver', 'chromedriver.exe') : path.join(__dirname, 'chromedriver', 'chromedriver');
 exports.version = '2.43';
-exports.start = function(args) {
+exports.start = function(args, returnPromise) {
   var cp = require('child_process').spawn(exports.path, args);
   cp.stdout.pipe(process.stdout);
   cp.stderr.pipe(process.stderr);
   exports.defaultInstance = cp;
-  return cp;
+  if (!returnPromise) {
+    return cp;
+  }
+  var port = getPortFromArgs(args);
+  var pollInterval = 100;
+  var timeout = 10000;
+  return tcpPortUsed.waitUntilUsed(port, pollInterval, timeout)
+    .then(function () {
+      return cp;
+    });
 };
 exports.stop = function () {
   if (exports.defaultInstance != null){

package.json

@@ -29,6 +29,7 @@
     "extract-zip": "^1.6.7",
     "kew": "^0.7.0",
     "mkdirp": "^0.5.1",
-    "request": "^2.87.0"
+    "request": "^2.87.0",
+    "tcp-port-used": "^1.0.0"
   }
 }