favor system typename hint.

Author: gmac

README.md

@@ -6,6 +6,12 @@ Testing GraphQL queries using fixture responses runs the risk of false-positive
 gem "graphql-response_validator"
 ```
 
+Then:
+
+```shell
+require "graphql/response_validator"
+```
+
 ## Usage
 
 Build a test query and its response data into a `GraphQL::ResponseValidator`, then assert that the fixture is correct for the query as part of your test:

lib/graphql/response_validator.rb

@@ -153,7 +153,7 @@ def validate_leaf(parent_type, value, path)
     def resolved_type(parent_type, data_part, path)
       return parent_type unless parent_type.kind.abstract?
 
-      typename = data_part["__typename"] || data_part[@system_typename]
+      typename = data_part[@system_typename] || data_part["__typename"]
       if typename.nil?
         @errors << ValidationError.new("Abstract position expects `__typename` or system typename hint", path.dup)
         return nil

lib/graphql/response_validator/version.rb

@@ -2,6 +2,6 @@
 
 module GraphQL
   class ResponseValidator
-    VERSION = "0.0.1"
+    VERSION = "0.0.2"
   end
 end