Updated the files.

my-app/node_modules/less/test/plugins/postprocess/index.js

@@ -0,0 +1,14 @@
+(function(exports) {
+    var postProcessor = function() {};
+
+    postProcessor.prototype = {
+        process: function (css) {
+            return 'hr {height:50px;}\n' + css;
+        }
+    };
+
+    exports.install = function(less, pluginManager) {
+        pluginManager.addPostProcessor( new postProcessor());
+    };
+
+})(typeof exports === 'undefined' ? this['postProcessorPlugin'] = {} : exports);