fix: ensure stubService returns reference to the service

Author: alexlafroscia

addon-test-support/stub-service.js

@@ -35,7 +35,7 @@ export default function stubService() {
     let [name] = arguments;
     let { owner } = getContext();
 
-    replace(owner, name);
+    return replace(owner, name);
   } else {
     throw new Error("Unexpected number of arguments");
   }

tests/unit/test-support/stub-service-test.js

@@ -18,14 +18,19 @@ module("Test Helpers | stub-service", function(hooks) {
 
   module("invoking without `hooks`", function(hooks) {
     hooks.beforeEach(function() {
-      stubService("to-stub");
+      this.service = stubService("to-stub");
     });
 
     test("it can replace a service", function(assert) {
       let service = this.owner.lookup("service:to-stub");
       service.method();
 
       assert.verify(service.method());
+      assert.equal(
+        service,
+        this.service,
+        "Returns a references to the stubbed service"
+      );
     });
   });
 });