Fix flow and unit test

src/validation/__tests__/KnownArgumentNames-test.js

@@ -109,7 +109,7 @@ describe('Validate: Known argument names', () => {
         dog @skip(unless: true)
       }
     `, [
-      unknownDirectiveArg('unless', 'skip', [], 3, 19),
+      unknownDirectiveArg('unless', 'skip', [ 'if' ], 3, 19),
     ]);
   });
 

src/validation/rules/KnownArgumentNames.js

@@ -53,6 +53,7 @@ export function unknownDirectiveArgMessage(
   } else {
     message += ' There is no known argument for this directive.';
   }
+  return message;
 }
 
 /**

src/validation/rules/KnownTypeNames.js

@@ -15,7 +15,7 @@ import { suggestionList } from '../../utilities/suggestionList';
 
 export function unknownTypeMessage(
   type: GraphQLType,
-  suggestedTypes: Arrray<string>
+  suggestedTypes: Array<string>
 ): string {
   let message = `Unknown type "${type}".`;
   const MAX_LENGTH = 5;