diff --git a/custom_components/versatile_thermostat/config_flow.py b/custom_components/versatile_thermostat/config_flow.py
index cebbe7d..078b3ce 100644
--- a/custom_components/versatile_thermostat/config_flow.py
+++ b/custom_components/versatile_thermostat/config_flow.py
@@ -331,7 +331,7 @@ class VersatileThermostatBaseConfigFlow(FlowHandler):
             }
         )
 
-    async def validate_input(self, data: dict) -> dict[str]:
+    async def validate_input(self, data: dict) -> None:
         """Validate the user input allows us to connect.
 
         Data has the keys from STEP_*_DATA_SCHEMA with values provided by the user.
diff --git a/custom_components/versatile_thermostat/requirements_dev.txt b/custom_components/versatile_thermostat/requirements_dev.txt
new file mode 100644
index 0000000..67296d7
--- /dev/null
+++ b/custom_components/versatile_thermostat/requirements_dev.txt
@@ -0,0 +1 @@
+homeassistant
\ No newline at end of file
diff --git a/custom_components/versatile_thermostat/requirements_test.txt b/custom_components/versatile_thermostat/requirements_test.txt
new file mode 100644
index 0000000..4a1fb9a
--- /dev/null
+++ b/custom_components/versatile_thermostat/requirements_test.txt
@@ -0,0 +1,3 @@
+# -r requirements_dev.txt
+# aiodiscover
+pytest-homeassistant-custom-component
\ No newline at end of file
diff --git a/custom_components/versatile_thermostat/tests/__init__.py b/custom_components/versatile_thermostat/tests/__init__.py
new file mode 100644
index 0000000..2203450
--- /dev/null
+++ b/custom_components/versatile_thermostat/tests/__init__.py
@@ -0,0 +1 @@
+""" To make this repo a module """
diff --git a/custom_components/versatile_thermostat/tests/conftest.py b/custom_components/versatile_thermostat/tests/conftest.py
new file mode 100644
index 0000000..01e5545
--- /dev/null
+++ b/custom_components/versatile_thermostat/tests/conftest.py
@@ -0,0 +1,52 @@
+"""Global fixtures for integration_blueprint integration."""
+# Fixtures allow you to replace functions with a Mock object. You can perform
+# many options via the Mock to reflect a particular behavior from the original
+# function that you want to see without going through the function's actual logic.
+# Fixtures can either be passed into tests as parameters, or if autouse=True, they
+# will automatically be used across all tests.
+#
+# Fixtures that are defined in conftest.py are available across all tests. You can also
+# define fixtures within a particular test file to scope them locally.
+#
+# pytest_homeassistant_custom_component provides some fixtures that are provided by
+# Home Assistant core. You can find those fixture definitions here:
+# https://github.com/MatthewFlamm/pytest-homeassistant-custom-component/blob/master/pytest_homeassistant_custom_component/common.py
+#
+# See here for more info: https://docs.pytest.org/en/latest/fixture.html (note that
+# pytest includes fixtures OOB which you can use as defined on this page)
+from unittest.mock import patch
+
+import pytest
+
+from custom_components.versatile_thermostat.config_flow import (
+    VersatileThermostatBaseConfigFlow,
+)
+
+pytest_plugins = "pytest_homeassistant_custom_component"
+
+
+# This fixture enables loading custom integrations in all tests.
+# Remove to enable selective use of this fixture
+@pytest.fixture(autouse=True)
+def auto_enable_custom_integrations(enable_custom_integrations):
+    yield
+
+
+# This fixture is used to prevent HomeAssistant from attempting to create and dismiss persistent
+# notifications. These calls would fail without this fixture since the persistent_notification
+# integration is never loaded during a test.
+@pytest.fixture(name="skip_notifications", autouse=True)
+def skip_notifications_fixture():
+    """Skip notification calls."""
+    with patch("homeassistant.components.persistent_notification.async_create"), patch(
+        "homeassistant.components.persistent_notification.async_dismiss"
+    ):
+        yield
+
+
+# This fixture is used to bypass the validate_input function in config_flow
+@pytest.fixture(name="skip_validate_input")
+def skip_validate_input_fixture():
+    """Skip the validate_input in config flow"""
+    with patch.object(VersatileThermostatBaseConfigFlow, "validate_input"):
+        yield
diff --git a/custom_components/versatile_thermostat/tests/const.py b/custom_components/versatile_thermostat/tests/const.py
new file mode 100644
index 0000000..0b07e0d
--- /dev/null
+++ b/custom_components/versatile_thermostat/tests/const.py
@@ -0,0 +1,71 @@
+from homeassistant.components.climate.const import (
+    PRESET_BOOST,
+    PRESET_COMFORT,
+    PRESET_ECO,
+)
+from custom_components.versatile_thermostat.const import (
+    CONF_NAME,
+    CONF_HEATER,
+    CONF_THERMOSTAT_CLIMATE,
+    CONF_THERMOSTAT_SWITCH,
+    CONF_THERMOSTAT_TYPE,
+    CONF_TEMP_SENSOR,
+    CONF_EXTERNAL_TEMP_SENSOR,
+    CONF_CYCLE_MIN,
+    CONF_TEMP_MAX,
+    CONF_TEMP_MIN,
+    CONF_PROP_FUNCTION,
+    PROPORTIONAL_FUNCTION_TPI,
+    CONF_TPI_COEF_INT,
+    CONF_TPI_COEF_EXT,
+    CONF_MINIMAL_ACTIVATION_DELAY,
+    CONF_SECURITY_DELAY_MIN,
+    CONF_SECURITY_MIN_ON_PERCENT,
+    CONF_SECURITY_DEFAULT_ON_PERCENT,
+    CONF_USE_WINDOW_FEATURE,
+    CONF_USE_MOTION_FEATURE,
+    CONF_USE_POWER_FEATURE,
+    CONF_USE_PRESENCE_FEATURE,
+)
+
+MOCK_TH_OVER_SWITCH_USER_CONFIG = {
+    CONF_NAME: "TheOverSwitchMockName",
+    CONF_THERMOSTAT_TYPE: CONF_THERMOSTAT_SWITCH,
+    CONF_TEMP_SENSOR: "sensor.mock_temp_sensor",
+    CONF_EXTERNAL_TEMP_SENSOR: "sensor.mock_ext_temp_sensor",
+    CONF_CYCLE_MIN: 5,
+    CONF_TEMP_MIN: 15,
+    CONF_TEMP_MAX: 30,
+    # Keep all additional optional features to false
+}
+
+MOCK_TH_OVER_SWITCH_TYPE_CONFIG = {
+    CONF_HEATER: "switch.mock_switch",
+    CONF_PROP_FUNCTION: PROPORTIONAL_FUNCTION_TPI,
+}
+
+MOCK_TH_OVER_SWITCH_TPI_CONFIG = {
+    CONF_TPI_COEF_INT: 0.3,
+    CONF_TPI_COEF_EXT: 0.1,
+}
+
+
+MOCK_PRESETS_CONFIG = {
+    PRESET_ECO + "_temp": 16,
+    PRESET_COMFORT + "_temp": 17,
+    PRESET_BOOST + "_temp": 18,
+}
+
+MOCK_ADVANCED_CONFIG = {
+    CONF_MINIMAL_ACTIVATION_DELAY: 10,
+    CONF_SECURITY_DELAY_MIN: 5,
+    CONF_SECURITY_MIN_ON_PERCENT: 0.4,
+    CONF_SECURITY_DEFAULT_ON_PERCENT: 0.3,
+}
+
+MOCK_DEFAULT_FEATURE_CONFIG = {
+    CONF_USE_WINDOW_FEATURE: False,
+    CONF_USE_MOTION_FEATURE: False,
+    CONF_USE_POWER_FEATURE: False,
+    CONF_USE_PRESENCE_FEATURE: False,
+}
diff --git a/custom_components/versatile_thermostat/tests/test_config_flow.py b/custom_components/versatile_thermostat/tests/test_config_flow.py
new file mode 100644
index 0000000..e0bc764
--- /dev/null
+++ b/custom_components/versatile_thermostat/tests/test_config_flow.py
@@ -0,0 +1,97 @@
+""" Test the Versatile Thermostat config flow """
+
+from homeassistant import data_entry_flow
+from homeassistant.core import HomeAssistant
+from homeassistant.config_entries import SOURCE_USER, ConfigEntry
+
+import pytest
+from pytest_homeassistant_custom_component.common import MockConfigEntry, load_fixture
+
+from custom_components.versatile_thermostat.const import DOMAIN
+from custom_components.versatile_thermostat import VersatileThermostatAPI
+
+from custom_components.versatile_thermostat.tests.const import (
+    MOCK_TH_OVER_SWITCH_USER_CONFIG,
+    MOCK_TH_OVER_SWITCH_TYPE_CONFIG,
+    MOCK_TH_OVER_SWITCH_TPI_CONFIG,
+    MOCK_PRESETS_CONFIG,
+    MOCK_ADVANCED_CONFIG,
+    MOCK_DEFAULT_FEATURE_CONFIG,
+)
+
+
+async def test_show_form(hass: HomeAssistant) -> None:
+    """Test that the form is served with no input"""
+    # Init the API
+    # hass.data["custom_components"] = None
+    # loader.async_get_custom_components(hass)
+    # VersatileThermostatAPI(hass)
+
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN, context={"source": SOURCE_USER}
+    )
+
+    assert result["type"] == data_entry_flow.RESULT_TYPE_FORM
+    assert result["step_id"] == SOURCE_USER
+
+
+async def test_user_config_flow_over_switch(hass, skip_validate_input):
+    """Test the config flow with thermostat_over_switch features"""
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN, context={"source": SOURCE_USER}
+    )
+
+    assert result["type"] == data_entry_flow.RESULT_TYPE_FORM
+    assert result["step_id"] == SOURCE_USER
+
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"], user_input=MOCK_TH_OVER_SWITCH_USER_CONFIG
+    )
+
+    assert result["type"] == data_entry_flow.RESULT_TYPE_FORM
+    assert result["step_id"] == "type"
+    assert result["errors"] == {}
+
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"], user_input=MOCK_TH_OVER_SWITCH_TYPE_CONFIG
+    )
+
+    assert result["type"] == data_entry_flow.RESULT_TYPE_FORM
+    assert result["step_id"] == "tpi"
+    assert result["errors"] == {}
+
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"], user_input=MOCK_TH_OVER_SWITCH_TPI_CONFIG
+    )
+
+    assert result["type"] == data_entry_flow.RESULT_TYPE_FORM
+    assert result["step_id"] == "presets"
+    assert result["errors"] == {}
+
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"], user_input=MOCK_PRESETS_CONFIG
+    )
+
+    assert result["type"] == data_entry_flow.RESULT_TYPE_FORM
+    assert result["step_id"] == "advanced"
+    assert result["errors"] == {}
+
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"], user_input=MOCK_ADVANCED_CONFIG
+    )
+
+    assert result["type"] == data_entry_flow.RESULT_TYPE_CREATE_ENTRY
+    assert (
+        result["data"]
+        == MOCK_TH_OVER_SWITCH_USER_CONFIG
+        | MOCK_TH_OVER_SWITCH_TYPE_CONFIG
+        | MOCK_TH_OVER_SWITCH_TPI_CONFIG
+        | MOCK_PRESETS_CONFIG
+        | MOCK_ADVANCED_CONFIG
+        | MOCK_DEFAULT_FEATURE_CONFIG
+    )
+    assert result["result"]
+    assert result["result"].domain == DOMAIN
+    assert result["result"].version == 1
+    assert result["result"].title == "TheOverSwitchMockName"
+    assert isinstance(result["result"], ConfigEntry)
diff --git a/custom_components/versatile_thermostat/tests/test_unittest.py b/custom_components/versatile_thermostat/tests/test_unittest.py
new file mode 100644
index 0000000..f217485
--- /dev/null
+++ b/custom_components/versatile_thermostat/tests/test_unittest.py
@@ -0,0 +1,14 @@
+import unittest  # The test framework
+
+
+class Test_TestIncrementDecrement(unittest.TestCase):
+    def test_increment(self):
+        self.assertEqual(4, 4)
+
+    # This test is designed to fail for demonstration purposes.
+    def test_decrement(self):
+        self.assertEqual(3, 3)
+
+
+if __name__ == "__main__":
+    unittest.main()