diff --git a/.coveragerc b/.coveragerc
index ff490303e47..c9038aafcb9 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -568,6 +568,12 @@ omit =
     homeassistant/components/mychevy/*
     homeassistant/components/mycroft/*
     homeassistant/components/mycroft/notify.py
+    homeassistant/components/mysensors/__init__.py
+    homeassistant/components/mysensors/const.py
+    homeassistant/components/mysensors/device.py
+    homeassistant/components/mysensors/handler.py
+    homeassistant/components/mysensors/helpers.py
+    homeassistant/components/mysensors/notify.py
     homeassistant/components/mysensors/binary_sensor.py
     homeassistant/components/mysensors/light.py
     homeassistant/components/mysensors/climate.py
diff --git a/homeassistant/components/mysensors/__init__.py b/homeassistant/components/mysensors/__init__.py
index 583508591fa..f1f139da857 100644
--- a/homeassistant/components/mysensors/__init__.py
+++ b/homeassistant/components/mysensors/__init__.py
@@ -1,4 +1,5 @@
 """Connect to a MySensors gateway via pymysensors API."""
+import asyncio
 import logging
 from typing import Callable, Dict, List, Optional, Tuple, Type, Union
 
@@ -199,8 +200,16 @@ async def async_unload_entry(hass: HomeAssistantType, entry: ConfigEntry) -> boo
         _LOGGER.error("Can't unload configentry %s, no gateway found", entry.entry_id)
         return False
 
-    for platform in SUPPORTED_PLATFORMS_WITH_ENTRY_SUPPORT:
-        await hass.config_entries.async_forward_entry_unload(entry, platform)
+    unload_ok = all(
+        await asyncio.gather(
+            *[
+                hass.config_entries.async_forward_entry_unload(entry, platform)
+                for platform in SUPPORTED_PLATFORMS_WITH_ENTRY_SUPPORT
+            ]
+        )
+    )
+    if not unload_ok:
+        return False
 
     key = MYSENSORS_ON_UNLOAD.format(entry.entry_id)
     if key in hass.data[DOMAIN]:
diff --git a/homeassistant/components/mysensors/manifest.json b/homeassistant/components/mysensors/manifest.json
index 8856fb5bc83..be201b97101 100644
--- a/homeassistant/components/mysensors/manifest.json
+++ b/homeassistant/components/mysensors/manifest.json
@@ -9,7 +9,8 @@
     "mqtt"
   ],
   "codeowners": [
-    "@MartinHjelmare", "@functionpointer"
+    "@MartinHjelmare",
+    "@functionpointer"
   ],
   "config_flow": true
-}
+}
\ No newline at end of file
diff --git a/homeassistant/components/mysensors/strings.json b/homeassistant/components/mysensors/strings.json
index 54113b502a1..402bc5848fe 100644
--- a/homeassistant/components/mysensors/strings.json
+++ b/homeassistant/components/mysensors/strings.json
@@ -2,13 +2,21 @@
   "title": "MySensors",
   "config": {
     "step": {
-      "confirm": {
-        "description": "[%key:common::config_flow::description::confirm_setup%]"
+      "user": {
+        "data": {
+          "host": "[%key:common::config_flow::data::host%]",
+          "username": "[%key:common::config_flow::data::username%]",
+          "password": "[%key:common::config_flow::data::password%]"
+        }
       }
     },
+    "error": {
+      "cannot_connect": "[%key:common::config_flow::error::cannot_connect%]",
+      "invalid_auth": "[%key:common::config_flow::error::invalid_auth%]",
+      "unknown": "[%key:common::config_flow::error::unknown%]"
+    },
     "abort": {
-      "single_instance_allowed": "[%key:common::config_flow::abort::single_instance_allowed%]",
-      "no_devices_found": "[%key:common::config_flow::abort::no_devices_found%]"
+      "already_configured": "[%key:common::config_flow::abort::already_configured_device%]"
     }
   }
 }
\ No newline at end of file
diff --git a/homeassistant/components/mysensors/translations/en.json b/homeassistant/components/mysensors/translations/en.json
index 0f1d9532459..873ed2ed721 100644
--- a/homeassistant/components/mysensors/translations/en.json
+++ b/homeassistant/components/mysensors/translations/en.json
@@ -1,58 +1,22 @@
 {
-  "config": {
-    "abort": {
-      "single_instance_allowed": "Already configured. Only a single configuration possible."
-    },
-    "error": {
-      "cannot_connect": "Failed to connect",
-      "invalid_subscribe_topic":  "Invalid subscribe topic",
-      "invalid_publish_topic": "Invalid publish topic",
-      "invalid_port": "Invalid port number",
-      "invalid_persistence_file": "Invalid persistence file",
-      "invalid_ip": "Invalid IP address",
-      "invalid_serial": "Invalid serial port",
-      "invalid_device": "Invalid device",
-      "invalid_version": "Invalid MySensors version",
-      "not_a_number": "Please enter a number",
-      "port_out_of_range": "Port number must be at least 1 and at most 65535"
-    },
-    "step": {
-      "user": {
-        "data": {
-          "optimistic": "optimistic",
-          "persistence": "persistence",
-          "gateway_type_mqtt": "MQTT"
+    "config": {
+        "abort": {
+            "already_configured": "Device is already configured"
         },
-        "description": "Choose connection method to the gateway"
-      },
-      "gw_tcp": {
-        "description": "Ethernet gateway setup",
-        "data": {
-          "device": "IP address of the gateway",
-          "tcp_port": "port",
-          "version": "MySensors version",
-          "persistence_file": "persistence file (leave empty to auto-generate)"
+        "error": {
+            "cannot_connect": "Failed to connect",
+            "invalid_auth": "Invalid authentication",
+            "unknown": "Unexpected error"
+        },
+        "step": {
+            "user": {
+                "data": {
+                    "host": "Host",
+                    "password": "Password",
+                    "username": "Username"
+                }
+            }
         }
-      },
-      "gw_serial": {
-        "description": "Serial gateway setup",
-        "data": {
-          "device": "Serial port",
-          "baud_rate": "baud rate",
-          "version": "MySensors version",
-          "persistence_file": "persistence file (leave empty to auto-generate)"
-        }
-      },
-      "gw_mqtt": {
-        "description": "MQTT gateway setup",
-        "data": {
-          "retain": "mqtt retain",
-          "topic_in_prefix": "prefix for input topics (topic_in_prefix)",
-          "topic_out_prefix": "prefix for output topics (topic_out_prefix)",
-          "version": "MySensors version",
-          "persistence_file": "persistence file (leave empty to auto-generate)"
-        }
-      }
-    }
-  }
+    },
+    "title": "MySensors"
 }
\ No newline at end of file
diff --git a/tests/components/mysensors/test_config_flow.py b/tests/components/mysensors/test_config_flow.py
new file mode 100644
index 00000000000..360e560a07b
--- /dev/null
+++ b/tests/components/mysensors/test_config_flow.py
@@ -0,0 +1,559 @@
+"""Test the MySensors config flow."""
+from typing import Dict
+from unittest.mock import patch
+
+import voluptuous as vol
+
+from homeassistant import config_entries, setup
+from homeassistant.components.mysensors import async_setup
+from homeassistant.components.mysensors.config_flow import MySensorsConfigFlowHandler
+from homeassistant.components.mysensors.const import (
+    CONF_BAUD_RATE,
+    CONF_DEVICE,
+    CONF_GATEWAY_TYPE,
+    CONF_GATEWAY_TYPE_MQTT,
+    CONF_GATEWAY_TYPE_SERIAL,
+    CONF_GATEWAY_TYPE_TCP,
+    CONF_GATEWAY_TYPE_TYPE,
+    CONF_GATEWAYS,
+    CONF_PERSISTENCE,
+    CONF_PERSISTENCE_FILE,
+    CONF_RETAIN,
+    CONF_TCP_PORT,
+    CONF_TOPIC_IN_PREFIX,
+    CONF_TOPIC_OUT_PREFIX,
+    CONF_VERSION,
+    DOMAIN,
+)
+from homeassistant.components.mysensors.gateway import is_serial_port
+from homeassistant.helpers.typing import ConfigType, HomeAssistantType
+
+
+async def get_form(
+    hass: HomeAssistantType, gatway_type: CONF_GATEWAY_TYPE_TYPE, expected_step_id: str
+):
+    """Get a form for the given gateway type."""
+    await setup.async_setup_component(hass, "persistent_notification", {})
+    stepuser = await hass.config_entries.flow.async_init(
+        DOMAIN, context={"source": config_entries.SOURCE_USER}
+    )
+    assert stepuser["type"] == "form"
+    assert not stepuser["errors"]
+
+    actualstep = await hass.config_entries.flow.async_configure(
+        stepuser["flow_id"],
+        {CONF_GATEWAY_TYPE: gatway_type},
+    )
+    await hass.async_block_till_done()
+    assert actualstep["type"] == "form"
+    assert actualstep["step_id"] == expected_step_id
+
+    return actualstep
+
+
+async def test_config_mqtt(hass: HomeAssistantType):
+    """Test configuring a mqtt gateway."""
+    step = await get_form(hass, CONF_GATEWAY_TYPE_MQTT, "gw_mqtt")
+    flowid = step["flow_id"]
+
+    with patch(
+        "homeassistant.components.mysensors.async_setup", return_value=True
+    ) as mock_setup, patch(
+        "homeassistant.components.mysensors.async_setup_entry",
+        return_value=True,
+    ) as mock_setup_entry:
+        result2 = await hass.config_entries.flow.async_configure(
+            flowid,
+            {
+                CONF_RETAIN: True,
+                CONF_TOPIC_IN_PREFIX: "bla",
+                CONF_TOPIC_OUT_PREFIX: "blub",
+                CONF_VERSION: "2.4",
+            },
+        )
+        await hass.async_block_till_done()
+
+    if "errors" in result2:
+        assert not result2["errors"]
+    assert result2["type"] == "create_entry"
+    assert result2["title"] == "mqtt"
+    assert result2["data"] == {
+        CONF_DEVICE: "mqtt",
+        CONF_RETAIN: True,
+        CONF_TOPIC_IN_PREFIX: "bla",
+        CONF_TOPIC_OUT_PREFIX: "blub",
+        CONF_VERSION: "2.4",
+    }
+    assert len(mock_setup.mock_calls) == 1
+    assert len(mock_setup_entry.mock_calls) == 1
+
+
+def test_is_serial_port_windows(hass: HomeAssistantType):
+    """Test windows serial ports."""
+    tests = {
+        "COM5": True,
+        "asdf": False,
+        "COM17": True,
+        "COM": False,
+        "/dev/ttyACM0": False,
+    }
+
+    def testport(port, result):
+        try:
+            is_serial_port(port)
+        except vol.Invalid:
+            success = False
+        else:
+            success = True
+        assert success == result
+
+    with patch("sys.platform", "win32"):
+        for test, result in tests.items():
+            testport(test, result)
+
+
+async def test_config_serial(hass: HomeAssistantType):
+    """Test configuring a gateway via serial."""
+    step = await get_form(hass, CONF_GATEWAY_TYPE_SERIAL, "gw_serial")
+    flowid = step["flow_id"]
+
+    with patch(  # mock is_serial_port because otherwise the test will be platform dependent (/dev/ttyACMx vs COMx)
+        "homeassistant.components.mysensors.config_flow.is_serial_port",
+        return_value=True,
+    ), patch(
+        "homeassistant.components.mysensors.config_flow.try_connect", return_value=True
+    ), patch(
+        "homeassistant.components.mysensors.async_setup", return_value=True
+    ) as mock_setup, patch(
+        "homeassistant.components.mysensors.async_setup_entry",
+        return_value=True,
+    ) as mock_setup_entry:
+        result2 = await hass.config_entries.flow.async_configure(
+            flowid,
+            {
+                CONF_BAUD_RATE: 115200,
+                CONF_DEVICE: "/dev/ttyACM0",
+                CONF_VERSION: "2.4",
+            },
+        )
+        await hass.async_block_till_done()
+
+    if "errors" in result2:
+        assert not result2["errors"]
+    assert result2["type"] == "create_entry"
+    assert result2["title"] == "/dev/ttyACM0"
+    assert result2["data"] == {
+        CONF_DEVICE: "/dev/ttyACM0",
+        CONF_BAUD_RATE: 115200,
+        CONF_VERSION: "2.4",
+    }
+    assert len(mock_setup.mock_calls) == 1
+    assert len(mock_setup_entry.mock_calls) == 1
+
+
+async def test_config_tcp(hass: HomeAssistantType):
+    """Test configuring a gateway via tcp."""
+    step = await get_form(hass, CONF_GATEWAY_TYPE_TCP, "gw_tcp")
+    flowid = step["flow_id"]
+
+    with patch(
+        "homeassistant.components.mysensors.config_flow.try_connect", return_value=True
+    ), patch(
+        "homeassistant.components.mysensors.async_setup", return_value=True
+    ) as mock_setup, patch(
+        "homeassistant.components.mysensors.async_setup_entry",
+        return_value=True,
+    ) as mock_setup_entry:
+        result2 = await hass.config_entries.flow.async_configure(
+            flowid,
+            {
+                CONF_TCP_PORT: 5003,
+                CONF_DEVICE: "127.0.0.1",
+                CONF_VERSION: "2.4",
+            },
+        )
+        await hass.async_block_till_done()
+
+    if "errors" in result2:
+        assert not result2["errors"]
+    assert result2["type"] == "create_entry"
+    assert result2["title"] == "127.0.0.1"
+    assert result2["data"] == {
+        CONF_DEVICE: "127.0.0.1",
+        CONF_TCP_PORT: 5003,
+        CONF_VERSION: "2.4",
+    }
+    assert len(mock_setup.mock_calls) == 1
+    assert len(mock_setup_entry.mock_calls) == 1
+
+
+async def test_fail_to_connect(hass: HomeAssistantType):
+    """Test configuring a gateway via tcp."""
+    step = await get_form(hass, CONF_GATEWAY_TYPE_TCP, "gw_tcp")
+    flowid = step["flow_id"]
+
+    with patch(
+        "homeassistant.components.mysensors.config_flow.try_connect", return_value=False
+    ), patch(
+        "homeassistant.components.mysensors.async_setup", return_value=True
+    ) as mock_setup, patch(
+        "homeassistant.components.mysensors.async_setup_entry",
+        return_value=True,
+    ) as mock_setup_entry:
+        result2 = await hass.config_entries.flow.async_configure(
+            flowid,
+            {
+                CONF_TCP_PORT: 5003,
+                CONF_DEVICE: "127.0.0.1",
+                CONF_VERSION: "2.4",
+            },
+        )
+        await hass.async_block_till_done()
+
+    assert result2["type"] == "form"
+    assert "errors" in result2
+    assert "base" in result2["errors"]
+    assert result2["errors"]["base"] == "cannot_connect"
+    assert len(mock_setup.mock_calls) == 0
+    assert len(mock_setup_entry.mock_calls) == 0
+
+
+async def config_invalid(
+    hass: HomeAssistantType,
+    gatway_type: CONF_GATEWAY_TYPE_TYPE,
+    expected_step_id: str,
+    user_input: Dict[str, any],
+    err_field,
+    err_string,
+):
+    """Perform a test that is expected to generate an error."""
+    step = await get_form(hass, gatway_type, expected_step_id)
+    flowid = step["flow_id"]
+
+    with patch(
+        "homeassistant.components.mysensors.config_flow.try_connect", return_value=True
+    ), patch(
+        "homeassistant.components.mysensors.async_setup", return_value=True
+    ) as mock_setup, patch(
+        "homeassistant.components.mysensors.async_setup_entry",
+        return_value=True,
+    ) as mock_setup_entry:
+        result2 = await hass.config_entries.flow.async_configure(
+            flowid,
+            user_input,
+        )
+        await hass.async_block_till_done()
+
+    assert result2["type"] == "form"
+    assert "errors" in result2
+    assert err_field in result2["errors"]
+    assert result2["errors"][err_field] == err_string
+    assert len(mock_setup.mock_calls) == 0
+    assert len(mock_setup_entry.mock_calls) == 0
+
+
+async def test_config_tcp_invalid_port(hass: HomeAssistantType):
+    """Test invalid port on a tcp gateway."""
+    await config_invalid(
+        hass,
+        CONF_GATEWAY_TYPE_TCP,
+        "gw_tcp",
+        {
+            CONF_TCP_PORT: 60000000,
+            CONF_DEVICE: "127.0.0.1",
+            CONF_VERSION: "2.4",
+        },
+        CONF_TCP_PORT,
+        "port_out_of_range",
+    )
+
+
+async def test_config_tcp_invalid_port_too_small(hass: HomeAssistantType):
+    """Test invalid port on a tcp gateway."""
+    await config_invalid(
+        hass,
+        CONF_GATEWAY_TYPE_TCP,
+        "gw_tcp",
+        {
+            CONF_TCP_PORT: 0,
+            CONF_DEVICE: "127.0.0.1",
+            CONF_VERSION: "2.4",
+        },
+        CONF_TCP_PORT,
+        "port_out_of_range",
+    )
+
+
+async def test_config_tcp_invalid_version(hass: HomeAssistantType):
+    """Test tcp gateway with invalid version."""
+    await config_invalid(
+        hass,
+        CONF_GATEWAY_TYPE_TCP,
+        "gw_tcp",
+        {
+            CONF_TCP_PORT: 5003,
+            CONF_DEVICE: "127.0.0.1",
+            CONF_VERSION: "a",
+        },
+        CONF_VERSION,
+        "invalid_version",
+    )
+
+
+async def test_config_tcp_invalid_version2(hass: HomeAssistantType):
+    """Test tcp gateway with invalid version."""
+    await config_invalid(
+        hass,
+        CONF_GATEWAY_TYPE_TCP,
+        "gw_tcp",
+        {
+            CONF_TCP_PORT: 5003,
+            CONF_DEVICE: "127.0.0.1",
+            CONF_VERSION: "a.b",
+        },
+        CONF_VERSION,
+        "invalid_version",
+    )
+
+
+async def test_config_tcp_no_version(hass: HomeAssistantType):
+    """Test tcp gateway with invalid version."""
+    await config_invalid(
+        hass,
+        CONF_GATEWAY_TYPE_TCP,
+        "gw_tcp",
+        {
+            CONF_TCP_PORT: 5003,
+            CONF_DEVICE: "127.0.0.1",
+        },
+        CONF_VERSION,
+        "invalid_version",
+    )
+
+
+async def test_config_tcp_invalid_address(hass: HomeAssistantType):
+    """Test tcp gateway with invalid ip address."""
+    await config_invalid(
+        hass,
+        CONF_GATEWAY_TYPE_TCP,
+        "gw_tcp",
+        {
+            CONF_TCP_PORT: 5003,
+            CONF_DEVICE: "127.0.0.",
+            CONF_VERSION: "2.4",
+        },
+        CONF_DEVICE,
+        "invalid_ip",
+    )
+
+
+async def test_config_mqtt_invalid_persistence_file(hass: HomeAssistantType):
+    """Test mqtt gateway with invalid input topic."""
+    await config_invalid(
+        hass,
+        CONF_GATEWAY_TYPE_MQTT,
+        "gw_mqtt",
+        {
+            CONF_RETAIN: True,
+            CONF_TOPIC_IN_PREFIX: "bla",
+            CONF_TOPIC_OUT_PREFIX: "blub",
+            CONF_PERSISTENCE_FILE: "asdf.zip",
+            CONF_VERSION: "2.4",
+        },
+        CONF_PERSISTENCE_FILE,
+        "invalid_persistence_file",
+    )
+
+
+async def test_config_mqtt_invalid_in_topic(hass: HomeAssistantType):
+    """Test mqtt gateway with invalid input topic."""
+    await config_invalid(
+        hass,
+        CONF_GATEWAY_TYPE_MQTT,
+        "gw_mqtt",
+        {
+            CONF_RETAIN: True,
+            CONF_TOPIC_IN_PREFIX: "/#/#",
+            CONF_TOPIC_OUT_PREFIX: "blub",
+            CONF_VERSION: "2.4",
+        },
+        CONF_TOPIC_IN_PREFIX,
+        "invalid_subscribe_topic",
+    )
+
+
+async def test_config_mqtt_invalid_out_topic(hass: HomeAssistantType):
+    """Test mqtt gateway with invalid output topic."""
+    await config_invalid(
+        hass,
+        CONF_GATEWAY_TYPE_MQTT,
+        "gw_mqtt",
+        {
+            CONF_RETAIN: True,
+            CONF_TOPIC_IN_PREFIX: "asdf",
+            CONF_TOPIC_OUT_PREFIX: "/#/#",
+            CONF_VERSION: "2.4",
+        },
+        CONF_TOPIC_OUT_PREFIX,
+        "invalid_publish_topic",
+    )
+
+
+async def attempt_import(hass: HomeAssistantType, config: ConfigType, expected_calls=1):
+    """Test importing a gateway."""
+    with patch("sys.platform", "win32"), patch(
+        "homeassistant.components.mysensors.config_flow.try_connect", return_value=True
+    ), patch(
+        "homeassistant.components.mysensors.async_setup_entry",
+        return_value=True,
+    ) as mock_setup_entry:
+        result = await async_setup(hass, config)
+        assert result
+        await hass.async_block_till_done()
+
+    assert len(mock_setup_entry.mock_calls) == expected_calls
+    return mock_setup_entry.call_args
+
+
+async def test_import_serial(hass: HomeAssistantType):
+    """Test importing a gateway via serial."""
+    args, _ = await attempt_import(
+        hass,
+        {
+            DOMAIN: {
+                CONF_GATEWAYS: [
+                    {
+                        CONF_DEVICE: "COM5",
+                        CONF_PERSISTENCE_FILE: "bla.json",
+                        CONF_BAUD_RATE: 57600,
+                        CONF_TCP_PORT: 5003,
+                    }
+                ],
+                CONF_VERSION: "2.3",
+                CONF_PERSISTENCE: False,
+                CONF_RETAIN: True,
+            }
+        },
+        1,
+    )
+    # check result
+    # we check in this weird way bc there may be some extra keys that we don't care about
+    wanted = {
+        CONF_GATEWAY_TYPE: CONF_GATEWAY_TYPE_SERIAL,
+        CONF_DEVICE: "COM5",
+        CONF_PERSISTENCE_FILE: "bla.json",
+        CONF_BAUD_RATE: 57600,
+        CONF_VERSION: "2.3",
+    }
+    for key, value in wanted.items():
+        assert key in args[1].data
+        assert args[1].data[key] == value
+
+
+async def test_import_tcp(hass: HomeAssistantType):
+    """Test configuring a gateway via serial."""
+    args, _ = await attempt_import(
+        hass,
+        {
+            DOMAIN: {
+                CONF_GATEWAYS: [
+                    {
+                        CONF_DEVICE: "127.0.0.1",
+                        CONF_PERSISTENCE_FILE: "blub.pickle",
+                        CONF_BAUD_RATE: 115200,
+                        CONF_TCP_PORT: 343,
+                    }
+                ],
+                CONF_VERSION: "2.4",
+                CONF_PERSISTENCE: False,
+                CONF_RETAIN: False,
+            }
+        },
+        1,
+    )
+    # check result
+    # we check in this weird way bc there may be some extra keys that we don't care about
+    wanted = {
+        CONF_GATEWAY_TYPE: CONF_GATEWAY_TYPE_TCP,
+        CONF_DEVICE: "127.0.0.1",
+        CONF_PERSISTENCE_FILE: "blub.pickle",
+        CONF_TCP_PORT: 343,
+        CONF_VERSION: "2.4",
+    }
+    for key, value in wanted.items():
+        assert key in args[1].data
+        assert args[1].data[key] == value
+
+
+async def test_import_mqtt(hass: HomeAssistantType):
+    """Test configuring a gateway via serial."""
+    args, _ = await attempt_import(
+        hass,
+        {
+            DOMAIN: {
+                CONF_GATEWAYS: [
+                    {
+                        CONF_DEVICE: "mqtt",
+                        CONF_BAUD_RATE: 115200,
+                        CONF_TCP_PORT: 5003,
+                        CONF_TOPIC_IN_PREFIX: "intopic",
+                        CONF_TOPIC_OUT_PREFIX: "outtopic",
+                    }
+                ],
+                CONF_VERSION: "2.4",
+                CONF_PERSISTENCE: False,
+                CONF_RETAIN: False,
+            }
+        },
+        1,
+    )
+    # check result
+    # we check in this weird way bc there may be some extra keys that we don't care about
+    wanted = {
+        CONF_GATEWAY_TYPE: CONF_GATEWAY_TYPE_MQTT,
+        CONF_DEVICE: "mqtt",
+        CONF_VERSION: "2.4",
+        CONF_TOPIC_OUT_PREFIX: "outtopic",
+        CONF_TOPIC_IN_PREFIX: "intopic",
+    }
+    for key, value in wanted.items():
+        assert key in args[1].data
+        assert args[1].data[key] == value
+
+
+async def test_import_two(hass: HomeAssistantType):
+    """Test configuring a gateway via serial."""
+    await attempt_import(
+        hass,
+        {
+            DOMAIN: {
+                CONF_GATEWAYS: [
+                    {
+                        CONF_DEVICE: "mqtt",
+                        CONF_PERSISTENCE_FILE: "bla.json",
+                        CONF_BAUD_RATE: 115200,
+                        CONF_TCP_PORT: 5003,
+                    },
+                    {
+                        CONF_DEVICE: "COM6",
+                        CONF_PERSISTENCE_FILE: "bla.json",
+                        CONF_BAUD_RATE: 115200,
+                        CONF_TCP_PORT: 5003,
+                    },
+                ],
+                CONF_VERSION: "2.4",
+                CONF_PERSISTENCE: False,
+                CONF_RETAIN: False,
+            }
+        },
+        2,
+    )
+
+
+async def test_validate_common_none(hass: HomeAssistantType):
+    """Test validate common with None."""
+    with patch("sys.platform", "win32"), patch(
+        "homeassistant.components.mysensors.config_flow.try_connect", return_value=True
+    ):
+        handler = MySensorsConfigFlowHandler()
+        assert await handler.validate_common(CONF_GATEWAY_TYPE_MQTT) == {}