allow runner to run sub tests

test/e2e/runner.js

@@ -7,16 +7,18 @@ var server = httpServer.createServer({
 server.listen(8080)
 
 var spawn = require('cross-spawn')
-var runner = spawn(
-  './node_modules/.bin/nightwatch',
-  [
-    '--config', 'build/nightwatch.config.js',
-    '--env', 'chrome,firefox'
-  ],
-  {
-    stdio: 'inherit'
-  }
-)
+var args = [
+  '--config', 'build/nightwatch.config.js',
+  '--env', 'chrome,firefox'
+]
+
+if (process.argv[2]) {
+  args.push('--test', 'test/e2e/specs/' + process.argv[2])
+}
+
+var runner = spawn('./node_modules/.bin/nightwatch', args, {
+  stdio: 'inherit'
+})
 
 runner.on('exit', function (code) {
   server.close()