Fix test helper setup to avoid error on ember-source@3.3.0+.

tests/helpers/resolver.js

@@ -1,11 +1,9 @@
 import Resolver from '../../resolver';
 import config from '../../config/environment';
 
-const resolver = Resolver.create();
-
-resolver.namespace = {
-  modulePrefix: config.modulePrefix,
-  podModulePrefix: config.podModulePrefix
-};
-
-export default resolver;
+export default Resolver.create({
+  namespace: {
+    modulePrefix: config.modulePrefix,
+    podModulePrefix: config.podModulePrefix,
+  },
+});