2 files changed, 6 insertions, 2 deletions
diff --git a/lab_control/test/jds6600_test.py b/lab_control/test/jds6600_test.py
index e9089c0..817ccf4 100644
--- a/lab_control/test/jds6600_test.py
+++ b/lab_control/test/jds6600_test.py
@@ -74,3 +74,4 @@ def test_invalidChannel(uut):
 
         with pytest.raises(AssertionError):
             uut.setOff(ch)
+
diff --git a/lab_control/test/mock_jds6600_device.py b/lab_control/test/mock_jds6600_device.py
index 6db4f4c..979ec69 100644
--- a/lab_control/test/mock_jds6600_device.py
+++ b/lab_control/test/mock_jds6600_device.py
@@ -69,11 +69,14 @@ class MockJDS6600Device():
                 shape = int(args[0])
                 self._channels[ch].function = shape
 
+            return ":ok\r\n"
+
         elif opcode == "r":
             if function == 20:
                 return f":r20={int(self._channels[0].on)},{int(self._channels[1].on)}.\r\n"
-
-        return ":ok\r\n"
+        
+        # Unknown request format, no response
+        return None
 
     def stop(self) -> None:
         self._masterFile.close()