test: Extract get_kind_from_index function and test it

Pull get_kind_from_index from class to module level and add tests.

Related #1097

lib/logitech_receiver/receiver.py

@@ -405,7 +405,7 @@ class Ex100Receiver(Receiver):
         assert notification.address == 0x02
         online = True
         encrypted = bool(notification.data[0] & 0x80)
-        kind = hidpp10_constants.DEVICE_KIND[self.get_kind_from_index(number)]
+        kind = hidpp10_constants.DEVICE_KIND[_get_kind_from_index(self, number)]
         wpid = "00" + notification.data[2:3].hex().upper()
         return online, encrypted, wpid, kind
 
@@ -414,10 +414,11 @@ class Ex100Receiver(Receiver):
         if not wpid:
             logger.error("Unable to get wpid from udev for device %d of %s", number, self)
             raise exceptions.NoSuchDevice(number=number, receiver=self, error="Not present 27Mhz device")
-        kind = hidpp10_constants.DEVICE_KIND[self.get_kind_from_index(number)]
+        kind = hidpp10_constants.DEVICE_KIND[_get_kind_from_index(self, number)]
         return {"wpid": wpid, "kind": kind, "polling": "", "serial": None, "power_switch": "(unknown)"}
 
-    def get_kind_from_index(self, index):
+
+def _get_kind_from_index(receiver, index):
     """Get device kind from 27Mhz device index"""
     # From drivers/hid/hid-logitech-dj.c
     if index == 1:  # mouse
@@ -429,8 +430,8 @@ class Ex100Receiver(Receiver):
     elif index == 4:  # numpad
         kind = 3
     else:  # unknown device number on 27Mhz receiver
-            logger.error("failed to calculate device kind for device %d of %s", index, self)
+        logger.error("failed to calculate device kind for device %d of %s", index, receiver)
-            raise exceptions.NoSuchDevice(number=index, receiver=self, error="Unknown 27Mhz device number")
+        raise exceptions.NoSuchDevice(number=index, receiver=receiver, error="Unknown 27Mhz device number")
     return kind
 
 

tests/logitech_receiver/test_receiver.py

@@ -0,0 +1,26 @@
+from unittest import mock
+
+import pytest
+
+from logitech_receiver import exceptions, receiver
+
+
+@pytest.mark.parametrize(
+    "index, expected_kind",
+    [
+        (0, None),
+        (1, 2),  # mouse
+        (2, 2),  # mouse
+        (3, 1),  # keyboard
+        (4, 3),  # numpad
+        (5, None),
+    ],
+)
+def test_get_kind_from_index(index, expected_kind):
+    mock_receiver = mock.Mock()
+
+    if expected_kind:
+        assert receiver._get_kind_from_index(mock_receiver, index) == expected_kind
+    else:
+        with pytest.raises(exceptions.NoSuchDevice):
+            receiver._get_kind_from_index(mock_receiver, index)