Add npm tests

.travis.yml

@@ -3,3 +3,8 @@ php:
   - '5.3'
   - '5.6'
   - '7.0'
+before_script:
+  - sudo apt-get update
+  - sudo apt-get install -y nodejs
+  - npm install -g gulp
+  - npm install

tests/Common/NpmTest.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace CommonTests;
+
+class NpmTest extends \PHPUnit_Framework_TestCase
+{
+	public function testJsValidate()
+	{
+		$out = array();
+		exec('gulp js:validate', $out);
+
+		$this->assertTrue(0 < \count($out));
+		$this->assertTrue(false === \strpos(\implode('|', $out), 'problem'));
+	}
+}