Add sinon-as-promised package for testing

Author: simonsmith

package.json

@@ -39,6 +39,7 @@
     "postcss-property-lookup": "^1.1.4",
     "rewire": "^2.5.1",
     "sinon": "^1.17.2",
+    "sinon-as-promised": "^4.0.0",
     "sinon-chai": "^2.8.0",
     "stylelint-config-suitcss": "^1.0.0"
   },

test/test.js

@@ -7,6 +7,7 @@ var rewire = require('rewire');
 var suitcss = rewire('../lib');
 var path = require('path');
 var sinonChai = require('sinon-chai');
+require('sinon-as-promised');
 
 chai.use(sinonChai);
 var expect = chai.expect;