Add test cases for Tradfri sensor platform (#64165)

* Add tests for Tradfri sensor platform

* Update docstring

tests/components/tradfri/test_sensor.py

@@ -0,0 +1,71 @@
+"""Tradfri sensor platform tests."""
+
+from unittest.mock import MagicMock, Mock
+
+from .common import setup_integration
+
+
+def mock_sensor(state_name: str, state_value: str, device_number=0):
+    """Mock a tradfri sensor."""
+    dev_info_mock = MagicMock()
+    dev_info_mock.manufacturer = "manufacturer"
+    dev_info_mock.model_number = "model"
+    dev_info_mock.firmware_version = "1.2.3"
+
+    # Set state value, eg battery_level = 50
+    setattr(dev_info_mock, state_name, state_value)
+
+    _mock_sensor = Mock(
+        id=f"mock-sensor-id-{device_number}",
+        reachable=True,
+        observe=Mock(),
+        device_info=dev_info_mock,
+        has_light_control=False,
+        has_socket_control=False,
+        has_blind_control=False,
+        has_signal_repeater_control=False,
+        has_air_purifier_control=False,
+    )
+    _mock_sensor.name = f"tradfri_sensor_{device_number}"
+
+    return _mock_sensor
+
+
+async def test_battery_sensor(hass, mock_gateway, mock_api_factory):
+    """Test that a battery sensor is correctly added."""
+    mock_gateway.mock_devices.append(
+        mock_sensor(state_name="battery_level", state_value=60)
+    )
+    await setup_integration(hass)
+
+    sensor_1 = hass.states.get("sensor.tradfri_sensor_0")
+    assert sensor_1 is not None
+    assert sensor_1.state == "60"
+    assert sensor_1.attributes["unit_of_measurement"] == "%"
+    assert sensor_1.attributes["device_class"] == "battery"
+
+
+async def test_sensor_observed(hass, mock_gateway, mock_api_factory):
+    """Test that sensors are correctly observed."""
+
+    sensor = mock_sensor(state_name="battery_level", state_value=60)
+    mock_gateway.mock_devices.append(sensor)
+    await setup_integration(hass)
+    assert len(sensor.observe.mock_calls) > 0
+
+
+async def test_sensor_available(hass, mock_gateway, mock_api_factory):
+    """Test sensor available property."""
+
+    sensor = mock_sensor(state_name="battery_level", state_value=60, device_number=1)
+    sensor.reachable = True
+
+    sensor2 = mock_sensor(state_name="battery_level", state_value=60, device_number=2)
+    sensor2.reachable = False
+
+    mock_gateway.mock_devices.append(sensor)
+    mock_gateway.mock_devices.append(sensor2)
+    await setup_integration(hass)
+
+    assert hass.states.get("sensor.tradfri_sensor_1").state == "60"
+    assert hass.states.get("sensor.tradfri_sensor_2").state == "unavailable"