test: starting testing client._handle_tx

colmi_r02_client/client.py

@@ -89,13 +89,17 @@ async def connect(self):
         assert rx_char
         self.rx_char = rx_char
 
-        await self.bleak_client.start_notify(UART_TX_CHAR_UUID, self.handle_tx)
+        await self.bleak_client.start_notify(UART_TX_CHAR_UUID, self._handle_tx)
 
     async def disconnect(self):
         await self.bleak_client.disconnect()
 
-    def handle_tx(self, _: BleakGATTCharacteristic, packet: bytearray) -> None:
+    def _handle_tx(self, _: BleakGATTCharacteristic, packet: bytearray) -> None:
+        """Bleak callback that handles new packets from the ring."""
+
         logger.info(f"Received packet {packet}")
+
+        assert len(packet) == 16, f"Packet is the wrong length {packet}"
         packet_type = packet[0]
         assert packet_type < 127, f"Packet has error bit set {packet}"
 

tests/test_client.py

@@ -0,0 +1,22 @@
+from unittest.mock import Mock
+import pytest
+
+from bleak.backends.characteristic import BleakGATTCharacteristic
+
+from colmi_r02_client.client import Client
+
+MOCK_CHAR = Mock(spec=BleakGATTCharacteristic)
+
+
+def test_handle_tx_short_packet():
+    client = Client("unused")
+
+    with pytest.raises(AssertionError, match="Packet is the wrong length"):
+        client._handle_tx(MOCK_CHAR, bytearray())
+
+
+def test_handle_tx_error_bit():
+    client = Client("unused")
+
+    with pytest.raises(AssertionError, match="Packet has error bit"):
+        client._handle_tx(MOCK_CHAR, bytearray(b"\xf1" * 16))