Added interface inheritance test. (#395)

Author: stefanospetrakis

tests/modules/graphql_plugin_test/src/Plugin/GraphQL/Fields/Engine.php

@@ -13,7 +13,7 @@
  *   secure = true,
  *   name = "engine",
  *   type = "String",
- *   types = {"Car"}
+ *   types = {"MotorizedVehicle"}
  * )
  */
 class Engine extends FieldPluginBase {

tests/modules/graphql_plugin_test/src/Plugin/GraphQL/Interfaces/MotorizedVehicle.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Drupal\graphql_plugin_test\Plugin\GraphQL\Interfaces;
+
+use Drupal\graphql\Plugin\GraphQL\Interfaces\InterfacePluginBase;
+
+/**
+ * Vehicle interface definition.
+ *
+ * @GraphQLInterface(
+ *   id = "motorized_vehicle",
+ *   name = "MotorizedVehicle",
+ *   interfaces = {"Vehicle"}
+ * )
+ */
+class MotorizedVehicle extends InterfacePluginBase {
+
+}

tests/modules/graphql_plugin_test/src/Plugin/GraphQL/Types/Car.php

@@ -10,7 +10,7 @@
  * @GraphQLType(
  *   id = "car",
  *   name = "Car",
- *   interfaces = {"Vehicle"},
+ *   interfaces = {"MotorizedVehicle"},
  * )
  */
 class Car extends TypePluginBase {