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

@@ -192,7 +192,7 @@ def device_pairing_information(self, n: int) -> dict:
             if not wpid:
                 logger.error("Unable to get wpid from udev for device %d of %s", n, self)
                 raise exceptions.NoSuchDevice(number=n, receiver=self, error="Not present 27Mhz device")
-            kind = hidpp10_constants.DEVICE_KIND[self.get_kind_from_index(n)]
+            kind = hidpp10_constants.DEVICE_KIND[get_kind_from_index(receiver=self, index=n)]
         elif not self.receiver_kind == "unifying":  # may be an old Nano receiver
             device_info = self.read_register(_R.receiver_info, 0x04)
             if device_info:
@@ -211,22 +211,6 @@ def device_pairing_information(self, n: int) -> dict:
             serial = pair_info[1:5].hex().upper()
         return {"wpid": wpid, "kind": kind, "polling": polling_rate, "serial": serial, "power_switch": power_switch}
 
-    def get_kind_from_index(self, index):
-        """Get device kind from 27Mhz device index"""
-        # From drivers/hid/hid-logitech-dj.c
-        if index == 1:  # mouse
-            kind = 2
-        elif index == 2:  # mouse
-            kind = 2
-        elif index == 3:  # keyboard
-            kind = 1
-        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)
-            raise exceptions.NoSuchDevice(number=index, receiver=self, error="Unknown 27Mhz device number")
-        return kind
-
     def notify_devices(self):
         """Scan all devices."""
         if self.handle:
@@ -396,3 +380,23 @@ def __str__(self):
     __repr__ = __str__
 
     __bool__ = __nonzero__ = lambda self: self.handle is not None
+
+
+def get_kind_from_index(
+    index: int,
+    receiver: Receiver,
+) -> int:
+    """Get device kind from 27Mhz device index"""
+    # From drivers/hid/hid-logitech-dj.c
+    if index == 1:  # mouse
+        kind = 2
+    elif index == 2:  # mouse
+        kind = 2
+    elif index == 3:  # keyboard
+        kind = 1
+    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, receiver)
+        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(index, mock_receiver) == expected_kind
+    else:
+        with pytest.raises(exceptions.NoSuchDevice):
+            receiver.get_kind_from_index(index, mock_receiver)