Fix connect_fail test and modbus.py 100% coverage (#57894)

Co-authored-by: Joakim Sørensen <joasoe@gmail.com>

.coveragerc

@@ -649,7 +649,6 @@ omit =
     homeassistant/components/mjpeg/camera.py
     homeassistant/components/mochad/*
     homeassistant/components/modbus/climate.py
-    homeassistant/components/modbus/modbus.py
     homeassistant/components/modem_callerid/sensor.py
     homeassistant/components/motion_blinds/__init__.py
     homeassistant/components/motion_blinds/const.py

homeassistant/components/modbus/modbus.py

@@ -386,7 +386,7 @@ class ModbusHub:
             return None
         async with self._lock:
             if not self._client:
-                return None
+                return None  # pragma: no cover
             result = await self.hass.async_add_executor_job(
                 self._pymodbus_call, unit, address, value, use_call
             )

tests/components/modbus/test_init.py

@@ -648,7 +648,7 @@ async def test_pymodbus_close_fail(hass, caplog, mock_pymodbus):
     # Close() is called as part of teardown
 
 
-async def test_pymodbus_connect_fail(hass, caplog):
+async def test_pymodbus_connect_fail(hass, caplog, mock_pymodbus):
     """Run test for failing pymodbus constructor."""
     config = {
         DOMAIN: [
@@ -660,14 +660,11 @@ async def test_pymodbus_connect_fail(hass, caplog):
             }
         ]
     }
-    with mock.patch(
-        "homeassistant.components.modbus.modbus.ModbusTcpClient", autospec=True
-    ) as mock_pb:
-        caplog.set_level(logging.ERROR)
-        exception_message = "test connect exception"
-        mock_pb.connect.side_effect = ModbusException(exception_message)
-
-        assert await async_setup_component(hass, DOMAIN, config) is True
+    caplog.set_level(logging.WARNING)
+    ExceptionMessage = "test connect exception"
+    mock_pymodbus.connect.side_effect = ModbusException(ExceptionMessage)
+    assert await async_setup_component(hass, DOMAIN, config) is False
+    assert ExceptionMessage in caplog.text
 
 
 async def test_delay(hass, mock_pymodbus):