diff --git a/.coveragerc b/.coveragerc
index a4288b278ca..5db28077014 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -651,10 +651,8 @@ omit =
     homeassistant/components/mitemp_bt/sensor.py
     homeassistant/components/mjpeg/camera.py
     homeassistant/components/mochad/*
-    homeassistant/components/modbus/base_platform.py
     homeassistant/components/modbus/climate.py
     homeassistant/components/modbus/modbus.py
-    homeassistant/components/modbus/validators.py
     homeassistant/components/modem_callerid/sensor.py
     homeassistant/components/motion_blinds/__init__.py
     homeassistant/components/motion_blinds/const.py
diff --git a/tests/components/modbus/test_init.py b/tests/components/modbus/test_init.py
index ba99df19b4d..b4657d7ee73 100644
--- a/tests/components/modbus/test_init.py
+++ b/tests/components/modbus/test_init.py
@@ -155,6 +155,13 @@ async def test_number_validator():
             CONF_DATA_TYPE: DATA_TYPE_INT,
             CONF_SWAP: CONF_SWAP_BYTE,
         },
+        {
+            CONF_NAME: TEST_ENTITY_NAME,
+            CONF_COUNT: 2,
+            CONF_DATA_TYPE: DATA_TYPE_CUSTOM,
+            CONF_STRUCTURE: ">i",
+            CONF_SWAP: CONF_SWAP_BYTE,
+        },
     ],
 )
 async def test_ok_struct_validator(do_config):
@@ -197,6 +204,13 @@ async def test_ok_struct_validator(do_config):
             CONF_STRUCTURE: ">f",
             CONF_SWAP: CONF_SWAP_WORD,
         },
+        {
+            CONF_NAME: TEST_ENTITY_NAME,
+            CONF_COUNT: 1,
+            CONF_DATA_TYPE: DATA_TYPE_STRING,
+            CONF_STRUCTURE: ">f",
+            CONF_SWAP: CONF_SWAP_WORD,
+        },
     ],
 )
 async def test_exception_struct_validator(do_config):
@@ -636,6 +650,34 @@ 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):
+    """Run test for failing pymodbus constructor."""
+    config = {
+        DOMAIN: [
+            {
+                CONF_NAME: TEST_MODBUS_NAME,
+                CONF_TYPE: TCP,
+                CONF_HOST: TEST_MODBUS_HOST,
+                CONF_PORT: TEST_PORT_TCP,
+            }
+        ]
+    }
+    with mock.patch(
+        "homeassistant.components.modbus.modbus.ModbusTcpClient", autospec=True
+    ) as mock_pb:
+        caplog.set_level(logging.ERROR)
+        ExceptionMessage = "test connect exception"
+        mock_pb.connect.side_effect = ModbusException(ExceptionMessage)
+
+        assert await async_setup_component(hass, DOMAIN, config) is True
+
+
+#        await hass.async_block_till_done()
+#        await hass.async_block_till_done()
+#        assert mock_pb.connect.called
+#        assert ExceptionMessage in caplog.text
+
+
 async def test_delay(hass, mock_pymodbus):
     """Run test for startup delay."""
 
diff --git a/tests/components/modbus/test_switch.py b/tests/components/modbus/test_switch.py
index c14a7169ae0..7e3c2d5f6c2 100644
--- a/tests/components/modbus/test_switch.py
+++ b/tests/components/modbus/test_switch.py
@@ -41,7 +41,13 @@ from homeassistant.core import State
 from homeassistant.setup import async_setup_component
 import homeassistant.util.dt as dt_util
 
-from .conftest import TEST_ENTITY_NAME, TEST_MODBUS_HOST, TEST_PORT_TCP, ReadResult
+from .conftest import (
+    TEST_ENTITY_NAME,
+    TEST_MODBUS_HOST,
+    TEST_PORT_TCP,
+    ReadResult,
+    do_next_cycle,
+)
 
 from tests.common import async_fire_time_changed
 
@@ -210,6 +216,45 @@ async def test_all_switch(hass, mock_do_cycle, expected):
     assert hass.states.get(ENTITY_ID).state == expected
 
 
+@pytest.mark.parametrize(
+    "do_config",
+    [
+        {
+            CONF_SWITCHES: [
+                {
+                    CONF_NAME: TEST_ENTITY_NAME,
+                    CONF_ADDRESS: 1234,
+                    CONF_SLAVE: 1,
+                    CONF_WRITE_TYPE: CALL_TYPE_REGISTER_HOLDING,
+                    CONF_SCAN_INTERVAL: 10,
+                    CONF_LAZY_ERROR: 2,
+                    CONF_VERIFY: {},
+                },
+            ],
+        },
+    ],
+)
+@pytest.mark.parametrize(
+    "register_words,do_exception,start_expect,end_expect",
+    [
+        (
+            [0x00],
+            True,
+            STATE_OFF,
+            STATE_UNAVAILABLE,
+        ),
+    ],
+)
+async def test_lazy_error_switch(hass, start_expect, end_expect, mock_do_cycle):
+    """Run test for given config."""
+    now = mock_do_cycle
+    assert hass.states.get(ENTITY_ID).state == start_expect
+    now = await do_next_cycle(hass, now, 11)
+    assert hass.states.get(ENTITY_ID).state == start_expect
+    now = await do_next_cycle(hass, now, 11)
+    assert hass.states.get(ENTITY_ID).state == end_expect
+
+
 @pytest.mark.parametrize(
     "mock_test_state",
     [(State(ENTITY_ID, STATE_ON),)],