Add test coverage for modbus switch (coil part) (#40696)

* Prepare test code for complex devices.

push entity_id to conftest, to make it common for all devices.

Add device to base_setup.

* Add test coverage for modbus switch (coil part).

* Update .coveragerc

* Update .coveragerc

Co-authored-by: Chris Talkington <chris@talkingtontech.com>

tests/components/modbus/test_modbus_switch.py

@@ -0,0 +1,59 @@
+"""The tests for the Modbus switch component."""
+from datetime import timedelta
+import logging
+
+from homeassistant.components.modbus.const import CALL_TYPE_COIL, CONF_COILS
+from homeassistant.components.switch import DOMAIN as SWITCH_DOMAIN
+from homeassistant.const import CONF_NAME, CONF_SLAVE
+
+from .conftest import run_base_read_test, setup_base_test
+
+_LOGGER = logging.getLogger(__name__)
+
+
+async def run_sensor_test(hass, use_mock_hub, value, expected):
+    """Run test for given config."""
+    switch_name = "modbus_test_switch"
+    scan_interval = 5
+    entity_id, now, device = await setup_base_test(
+        switch_name,
+        hass,
+        use_mock_hub,
+        {
+            CONF_COILS: [
+                {CONF_NAME: switch_name, CALL_TYPE_COIL: 1234, CONF_SLAVE: 1},
+            ]
+        },
+        SWITCH_DOMAIN,
+        scan_interval,
+    )
+
+    await run_base_read_test(
+        entity_id,
+        hass,
+        use_mock_hub,
+        CALL_TYPE_COIL,
+        value,
+        expected,
+        now + timedelta(seconds=scan_interval + 1),
+    )
+
+
+async def test_read_coil_false(hass, mock_hub):
+    """Test reading of switch coil."""
+    await run_sensor_test(
+        hass,
+        mock_hub,
+        [0x00],
+        expected="off",
+    )
+
+
+async def test_read_coil_true(hass, mock_hub):
+    """Test reading of switch coil."""
+    await run_sensor_test(
+        hass,
+        mock_hub,
+        [0xFF],
+        expected="on",
+    )