Added some tests

snippets/bindAll.md

@@ -6,8 +6,8 @@ Use `Array.forEach()` to return a `function` that uses `Function.apply()` to app
 const bindAll = (obj, ...fns) =>
   fns.forEach(
     fn =>
-      (obj[fn] = function() {
-        return fn.apply(obj);
+      (f = obj[fn], obj[fn] = function() {
+        return f.apply(obj);
       })
   );
 ```