diff --git a/packages/core/src/tests/CallbackManager.test.ts b/packages/core/src/tests/CallbackManager.test.ts
index 5e453b712acb915a625b7f486907dfcee0974b3b..772b9d85eb7800860da5dd700b6eb2f3778d087d 100644
--- a/packages/core/src/tests/CallbackManager.test.ts
+++ b/packages/core/src/tests/CallbackManager.test.ts
@@ -8,7 +8,11 @@ import {
   RetrievalCallbackResponse,
   StreamCallbackResponse,
 } from "../callbacks/CallbackManager";
-import { ListIndex } from "../index/list";
+import { ListIndex, ListRetrieverMode } from "../index/list";
+import {
+  ResponseSynthesizer,
+  SimpleResponseBuilder,
+} from "../ResponseSynthesizer";
 import { mockEmbeddingModel, mockLlmGeneration } from "./utility/mockOpenAI";
 
 // Mock the OpenAI getOpenAISession function during testing
@@ -138,10 +142,19 @@ describe("CallbackManager: onLLMStream and onRetrieve", () => {
       documents: [document],
       serviceContext,
     });
-    const queryEngine = listIndex.asQueryEngine();
+    const responseBuilder = new SimpleResponseBuilder(serviceContext);
+    const responseSynthesizer = new ResponseSynthesizer({
+      serviceContext: serviceContext,
+      responseBuilder,
+    });
+    const queryEngine = listIndex.asQueryEngine(
+      ListRetrieverMode.DEFAULT,
+      responseSynthesizer
+    );
     const query = "What is the author's name?";
     const response = await queryEngine.aquery(query);
     expect(response.toString()).toBe("MOCK_TOKEN_1-MOCK_TOKEN_2");
+    console.log(JSON.stringify(streamCallbackData, null, 2));
     expect(streamCallbackData).toEqual([
       {
         event: {