Fix tests

Author: djhi

src/introspection/getTypeFromValues.spec.js

@@ -7,7 +7,7 @@ import {
     GraphQLNonNull,
     GraphQLString,
 } from 'graphql';
-import GraphQLJSON from 'graphql-type-json';
+import { GraphQLJSON } from 'graphql-type-json';
 import DateType from './DateType';
 import getTypeFromValues from './getTypeFromValues';