Accept resolvers given by the user as is

tests/Language/GraphQL/SchemaSpec.hs

@@ -0,0 +1,31 @@
+{-# LANGUAGE OverloadedStrings #-}
+module Language.GraphQL.SchemaSpec
+    ( spec
+    ) where
+
+import qualified Data.Aeson as Aeson
+import qualified Data.Aeson.Types as Aeson
+import qualified Data.Sequence as Sequence
+import Data.Text (Text)
+import Language.GraphQL.AST.Core
+import Language.GraphQL.Error
+import Language.GraphQL.Schema
+import Test.Hspec (Spec, describe, it, shouldBe)
+
+spec :: Spec
+spec =
+    describe "resolve" $
+        it "ignores invalid __typename" $ do
+            let resolver = object "__typename" $ pure
+                    [ scalar "field" $ pure ("T" :: Text)
+                    ]
+                schema = resolversToMap [resolver]
+                fields = Sequence.singleton
+                    $ SelectionFragment
+                    $ Fragment "T" Sequence.empty
+                expected = Aeson.object
+                    [ ("data" , Aeson.emptyObject)
+                    ]
+
+            actual <- runCollectErrs (resolve schema fields)
+            actual `shouldBe` expected