Add transport layer tests

src/py_dvt_ate/instruments/transport/tcp.py

@@ -147,6 +147,8 @@ class TCPTransport:
             # Decode and strip whitespace
             return response_bytes.decode(self._encoding).strip()
 
+        except ConnectionError:
+            raise  # Re-raise ConnectionError as-is
         except socket.timeout as err:
             raise TimeoutError("Read timeout") from err
         except (socket.error, OSError, UnicodeDecodeError) as err: