fix test

Author: jdneo

lib/core.js

@@ -90,7 +90,7 @@ core.getProblem = function(keyword, cb) {
     if (e) return cb(e);
 
     const problem = problems.find(function(x) {
-      return x.fid + '' === keyword || x.name === keyword || x.slug === keyword;
+      return x.fid + '' === keyword + '' || x.name === keyword || x.slug === keyword;
     });
     if (!problem) return cb('Problem not found!');
     core.next.getProblem(problem, cb);