add mutate script

package.json

@@ -15,6 +15,7 @@
   "scripts": {
     "lint": "eslint .",
     "test": "nyc ava",
-    "ci": "yarn && node jenkins.js"
+    "ci": "yarn && node jenkins.js",
+    "mutate": "stryker run"
   }
 }

test/index.js

@@ -40,3 +40,14 @@ test ('copy object', (t) => {
   t.is (copy.foo, 'baz');
   t.is (obj.foo, 'bar');
 });
+
+test ('run regex', (t) => {
+  const data = 'foobarfoo';
+  const regex = /foo/gu;
+  let count = 0;
+  util.run_regex(regex,data,(res)=>{
+    t.is(res[0], 'foo');
+    count++;
+  })
+  t.is(count, 2);
+});