diff --git a/tmtc/test.py b/tmtc/test.py
index 75603f6..87f6b6b 100644
--- a/tmtc/test.py
+++ b/tmtc/test.py
@@ -53,7 +53,11 @@ def pack_test_command(p: ServiceProviderParams):
             if data_size < 0 or data_size > 1024:
                 print("Invalid data size")
             break
-        dummy_data = bytes(data_size)
+        dummy_data = bytearray()
+        next_byte = True
+        for i in range(data_size):
+            dummy_data.append(int(next_byte))
+            next_byte = not next_byte
         q.add_pus_tc(
             PusTelecommand(
                 service=PusServices.S17_TEST, subservice=130, app_data=dummy_data