diff --git a/tests/gcodeSender.py b/tests/gcodeSender.py
index d1c79ae62..764337a59 100755
--- a/tests/gcodeSender.py
+++ b/tests/gcodeSender.py
@@ -23,6 +23,8 @@ from pyMarlin   import *
 
 import argparse
 import serial
+import random
+import sys
 
 def load_gcode(filename):
   with open(filename, "r") as f:
@@ -30,8 +32,19 @@ def load_gcode(filename):
   print("Read %d lines" % len(gcode))
   return gcode
 
+def generate_synthetic_gcode():
+  gcode = []
+  non_acting_gcodes = ["G90", "G91", "G92 X0 Y0 Z0", "G92 X123 Y456", "M31", "M114", "M115", "M119"]
+  for i in range(1, 10000):
+    which = random.randrange(0,len(non_acting_gcodes))
+    gcode.append(non_acting_gcodes[which])
+  return gcode
+
 def send_gcode_test(filename, serial):
-  gcode = load_gcode(filename);
+  if filename == "TEST":
+    gcode = generate_synthetic_gcode()
+  else:
+    gcode = load_gcode(filename)
 
   for i, line in enumerate(gcode):
     serial.sendCommand(line)
@@ -39,6 +52,7 @@ def send_gcode_test(filename, serial):
       serial.readLine()
     if(i % 1000 == 0):
       print("Progress: %d" % (i*100/len(gcode)), end='\r')
+      sys.stdout.flush()
 
 parser = argparse.ArgumentParser(description='''sends gcode to a printer while injecting errors to test error recovery.''')
 parser.add_argument('-p', '--port',   help='Serial port.', default='/dev/ttyACM1')
@@ -46,7 +60,7 @@ parser.add_argument('-f', '--fake',   help='Use a fake Marlin simulation instead
 parser.add_argument('-e', '--errors', help='Corrupt 1 out N lines to exercise error recovery.', default='0', type=int)
 parser.add_argument('-l', '--log',    help='Write log file.')
 parser.add_argument('-b', '--baud',   help='Sets the baud rate for the serial port.', default='115000', type=int)
-parser.add_argument('filename',       help='file containing gcode.')
+parser.add_argument('filename',       help='file containing gcode, or TEST for synthetic non-printing GCODE')
 args = parser.parse_args()
 
 print()