diff --git a/core/src/main/java/com/google/adk/runner/Runner.java b/core/src/main/java/com/google/adk/runner/Runner.java
index e047d1e6..f8b94c72 100644
--- a/core/src/main/java/com/google/adk/runner/Runner.java
+++ b/core/src/main/java/com/google/adk/runner/Runner.java
@@ -135,7 +135,7 @@ public Builder eventsCompactionConfig(EventsCompactionConfig eventsCompactionCon
 
     public Runner build() {
       if (agent == null) {
-        throw new IllegalStateException("Agent must be provided.");
+        throw new IllegalStateException("Agent must be provided. Test - do not submit");
       }
       if (appName == null) {
         throw new IllegalStateException("App name must be provided.");