diff --git a/poetry.lock b/poetry.lock
index 79210f0..2e4abc3 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,4 +1,4 @@
-# This file is automatically @generated by Poetry 1.8.5 and should not be changed by hand.
+# This file is automatically @generated by Poetry 1.8.3 and should not be changed by hand.
 
 [[package]]
 name = "aioesphomeapi"
@@ -1260,6 +1260,24 @@ pluggy = ">=1.5,<2"
 [package.extras]
 dev = ["argcomplete", "attrs (>=19.2)", "hypothesis (>=3.56)", "mock", "pygments (>=2.7.2)", "requests", "setuptools", "xmlschema"]
 
+[[package]]
+name = "pytest-asyncio"
+version = "0.25.0"
+description = "Pytest support for asyncio"
+optional = false
+python-versions = ">=3.9"
+files = [
+    {file = "pytest_asyncio-0.25.0-py3-none-any.whl", hash = "sha256:db5432d18eac6b7e28b46dcd9b69921b55c3b1086e85febfe04e70b18d9e81b3"},
+    {file = "pytest_asyncio-0.25.0.tar.gz", hash = "sha256:8c0610303c9e0442a5db8604505fc0f545456ba1528824842b37b4a626cbf609"},
+]
+
+[package.dependencies]
+pytest = ">=8.2,<9"
+
+[package.extras]
+docs = ["sphinx (>=5.3)", "sphinx-rtd-theme (>=1)"]
+testing = ["coverage (>=6.2)", "hypothesis (>=5.7.1)"]
+
 [[package]]
 name = "pytest-codspeed"
 version = "3.1.0"
@@ -2177,4 +2195,4 @@ ifaddr = ">=0.1.7"
 [metadata]
 lock-version = "2.0"
 python-versions = ">=3.11,<3.14"
-content-hash = "209da2bd3753a6511f9ef29528f43880f0d36b8457f7eee88babcef6549eec00"
+content-hash = "f30ec8057cccd6d61b19eaeb3a48ffd6618aad064e5ac76e1827a965cc217388"
diff --git a/pyproject.toml b/pyproject.toml
index 9ff22da..fa169e4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -34,6 +34,8 @@ lru-dict = ">=1.2.0"
 pytest = ">=7,<9"
 pytest-cov = ">=3,<7"
 pytest-codspeed = "^3.1.0"
+zeroconf = "^0.136.2"
+pytest-asyncio = "^0.25.0"
 
 [tool.poetry.group.docs]
 optional = true
diff --git a/tests/__init__.py b/tests/__init__.py
index e69de29..38d4eda 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -0,0 +1,31 @@
+from typing import Any
+
+from bleak.backends.scanner import BLEDevice
+
+BLE_DEVICE_DEFAULTS = {
+    "name": None,
+    "rssi": -127,
+    "details": None,
+}
+
+
+def generate_ble_device(
+    address: str | None = None,
+    name: str | None = None,
+    details: Any | None = None,
+    rssi: int | None = None,
+    **kwargs: Any,
+) -> BLEDevice:
+    """Generate a BLEDevice with defaults."""
+    new = kwargs.copy()
+    if address is not None:
+        new["address"] = address
+    if name is not None:
+        new["name"] = name
+    if details is not None:
+        new["details"] = details
+    if rssi is not None:
+        new["rssi"] = rssi
+    for key, value in BLE_DEVICE_DEFAULTS.items():
+        new.setdefault(key, value)
+    return BLEDevice(**new)
diff --git a/tests/backend/test_client.py b/tests/backend/test_client.py
new file mode 100644
index 0000000..092bb75
--- /dev/null
+++ b/tests/backend/test_client.py
@@ -0,0 +1,299 @@
+from unittest.mock import patch
+from uuid import UUID
+
+import pytest
+from aioesphomeapi import (
+    APIClient,
+    APIVersion,
+    BluetoothGATTCharacteristic,
+    BluetoothGATTDescriptor,
+    BluetoothGATTService,
+    BluetoothProxyFeature,
+    DeviceInfo,
+    ESPHomeBluetoothGATTServices,
+)
+from bleak.exc import BleakError
+from habluetooth import BaseHaRemoteScanner, HaBluetoothConnector
+from pytest_asyncio import fixture as aio_fixture
+
+from bleak_esphome.backend.cache import ESPHomeBluetoothCache
+from bleak_esphome.backend.client import ESPHomeClient, ESPHomeClientData
+from bleak_esphome.backend.device import ESPHomeBluetoothDevice
+from bleak_esphome.backend.scanner import ESPHomeScanner
+
+from .. import generate_ble_device
+
+ESP_MAC_ADDRESS = "AA:BB:CC:DD:EE:FF"
+ESP_NAME = "proxy"
+
+
+def split_uuid(uuid: str) -> list[int]:
+    int_128 = UUID(uuid).int
+    return [int_128 >> 64, int_128 & 0xFFFFFFFFFFFFFFFF]
+
+
+@pytest.fixture
+def esphome_bluetooth_gatt_services() -> ESPHomeBluetoothGATTServices:
+
+    service1 = BluetoothGATTService(
+        uuid=split_uuid("00001800-0000-1000-8000-00805f9b34fb"),
+        handle=1,
+        characteristics=[],
+    )
+    object.__setattr__(
+        service1,
+        "characteristics",
+        [
+            BluetoothGATTCharacteristic(
+                uuid=split_uuid("00002a00-0000-1000-8000-00805f9b34fb"),
+                handle=3,
+                properties=2,
+                descriptors=[],
+            ),
+            BluetoothGATTCharacteristic(
+                uuid=split_uuid("00002a01-0000-1000-8000-00805f9b34fb"),
+                handle=5,
+                properties=2,
+                descriptors=[],
+            ),
+        ],
+    )
+    service2 = BluetoothGATTService(
+        uuid=split_uuid("00001801-0000-1000-8000-00805f9b34fb"),
+        handle=6,
+        characteristics=[],
+    )
+    service2_chars = [
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("00002a05-0000-1000-8000-00805f9b34fb"),
+            handle=8,
+            properties=32,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("00002b3a-0000-1000-8000-00805f9b34fb"),
+            handle=11,
+            properties=2,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("00002b29-0000-1000-8000-00805f9b34fb"),
+            handle=13,
+            properties=10,
+            descriptors=[],
+        ),
+    ]
+    object.__setattr__(
+        service2_chars[0],
+        "descriptors",
+        [
+            BluetoothGATTDescriptor(
+                uuid=split_uuid("00002902-0000-1000-8000-00805f9b34fb"),
+                handle=9,
+            )
+        ],
+    )
+    object.__setattr__(service2, "characteristics", service2_chars)
+
+    service3 = BluetoothGATTService(
+        uuid=split_uuid("d30a7847-e12b-09a8-b04b-8e0922a9abab"),
+        handle=14,
+        characteristics=[],
+    )
+    service3_chars = [
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("030b7847-e12b-09a8-b04b-8e0922a9abab"),
+            handle=16,
+            properties=2,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("040b7847-e12b-09a8-b04b-8e0922a9abab"),
+            handle=18,
+            properties=2,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("090b7847-e12b-09a8-b04b-8e0922a9abab"),
+            handle=20,
+            properties=10,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("050b7847-e12b-09a8-b04b-8e0922a9abab"),
+            handle=22,
+            properties=10,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("060b7847-e12b-09a8-b04b-8e0922a9abab"),
+            handle=24,
+            properties=8,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("070b7847-e12b-09a8-b04b-8e0922a9abab"),
+            handle=26,
+            properties=8,
+            descriptors=[],
+        ),
+    ]
+    object.__setattr__(service3, "characteristics", service3_chars)
+    service4 = BluetoothGATTService(
+        uuid=split_uuid("0000180a-0000-1000-8000-00805f9b34fb"),
+        handle=27,
+        characteristics=[],
+    )
+    service4_chars = [
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("00002a29-0000-1000-8000-00805f9b34fb"),
+            handle=29,
+            properties=2,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("00002a24-0000-1000-8000-00805f9b34fb"),
+            handle=31,
+            properties=2,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("00002a25-0000-1000-8000-00805f9b34fb"),
+            handle=33,
+            properties=2,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("00002a26-0000-1000-8000-00805f9b34fb"),
+            handle=35,
+            properties=2,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("00002a27-0000-1000-8000-00805f9b34fb"),
+            handle=37,
+            properties=2,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("00002a28-0000-1000-8000-00805f9b34fb"),
+            handle=39,
+            properties=2,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("0a0b7847-e12b-09a8-b04b-8e0922a9abab"),
+            handle=41,
+            properties=10,
+            descriptors=[],
+        ),
+        BluetoothGATTCharacteristic(
+            uuid=split_uuid("0b0b7847-e12b-09a8-b04b-8e0922a9abab"),
+            handle=43,
+            properties=10,
+            descriptors=[],
+        ),
+    ]
+    object.__setattr__(service4, "characteristics", service4_chars)
+    return ESPHomeBluetoothGATTServices(
+        address=57911560448430,
+        services=[service1, service2, service3, service4],
+    )
+
+
+def test_get_services() -> None:
+    connector = HaBluetoothConnector(ESPHomeClientData, ESP_MAC_ADDRESS, lambda: True)
+    scanner = ESPHomeScanner(ESP_MAC_ADDRESS, ESP_NAME, connector, True)
+    assert isinstance(scanner, BaseHaRemoteScanner)
+
+
+@aio_fixture(name="client_data")
+async def client_data_fixture(mock_client: APIClient) -> ESPHomeClientData:
+    """Return a client data fixture."""
+    connector = HaBluetoothConnector(ESPHomeClientData, ESP_MAC_ADDRESS, lambda: True)
+    return ESPHomeClientData(
+        bluetooth_device=ESPHomeBluetoothDevice(ESP_NAME, ESP_MAC_ADDRESS),
+        cache=ESPHomeBluetoothCache(),
+        client=mock_client,
+        device_info=DeviceInfo(
+            mac_address=ESP_MAC_ADDRESS,
+            name=ESP_NAME,
+            bluetooth_proxy_feature_flags=BluetoothProxyFeature.PASSIVE_SCAN
+            | BluetoothProxyFeature.ACTIVE_CONNECTIONS
+            | BluetoothProxyFeature.REMOTE_CACHING
+            | BluetoothProxyFeature.PAIRING
+            | BluetoothProxyFeature.CACHE_CLEARING
+            | BluetoothProxyFeature.RAW_ADVERTISEMENTS,
+        ),
+        api_version=APIVersion(1, 9),
+        title=ESP_NAME,
+        scanner=ESPHomeScanner(ESP_MAC_ADDRESS, ESP_NAME, connector, True),
+    )
+
+
+@pytest.mark.asyncio
+async def test_client_usage_while_not_connected(client_data: ESPHomeClientData) -> None:
+    """Test client usage while not connected."""
+    ble_device = generate_ble_device(
+        "CC:BB:AA:DD:EE:FF", details={"source": ESP_MAC_ADDRESS, "address_type": 1}
+    )
+
+    client = ESPHomeClient(ble_device, client_data=client_data)
+    with pytest.raises(
+        BleakError, match=f"{ESP_NAME}.*{ESP_MAC_ADDRESS}.*not connected"
+    ):
+        await client.write_gatt_char("test", b"test")
+
+
+@pytest.mark.asyncio
+async def test_client_get_services_and_write(
+    client_data: ESPHomeClientData,
+    esphome_bluetooth_gatt_services: ESPHomeBluetoothGATTServices,
+) -> None:
+    """Test getting client services and writing a GATT char."""
+    ble_device = generate_ble_device(
+        "CC:BB:AA:DD:EE:FF", details={"source": ESP_MAC_ADDRESS, "address_type": 1}
+    )
+
+    client = ESPHomeClient(ble_device, client_data=client_data)
+    client._is_connected = True
+    with patch.object(
+        client._client,
+        "bluetooth_gatt_get_services",
+        return_value=esphome_bluetooth_gatt_services,
+    ):
+        services = await client.get_services()
+
+    assert services is not None
+
+    char = client._resolve_characteristic(
+        char_specifier="090b7847-e12b-09a8-b04b-8e0922a9abab",
+    )
+    assert char is not None
+    assert char.uuid == "090b7847-e12b-09a8-b04b-8e0922a9abab"
+    assert char.properties == ["read", "write"]
+    assert char.handle == 20
+
+    char2 = services.get_characteristic("090b7847-e12b-09a8-b04b-8e0922a9abab")
+    assert char2 is not None
+    assert char2.uuid == "090b7847-e12b-09a8-b04b-8e0922a9abab"
+    assert char2.properties == ["read", "write"]
+    assert char2.handle == 20
+
+    char3 = services.get_characteristic(UUID("090b7847-e12b-09a8-b04b-8e0922a9abab"))
+    assert char3 is not None
+    assert char3.uuid == "090b7847-e12b-09a8-b04b-8e0922a9abab"
+    assert char3.properties == ["read", "write"]
+    assert char3.handle == 20
+
+    with patch.object(
+        client._client,
+        "bluetooth_gatt_write",
+    ) as mock_write:
+        await client.write_gatt_char(
+            "090b7847-e12b-09a8-b04b-8e0922a9abab",
+            b"test",
+            True,
+        )
+
+    mock_write.assert_called_once_with(225106397622015, 20, b"test", True)
diff --git a/tests/conftest.py b/tests/conftest.py
index fd5ca8c..b3a7aba 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,10 +1,19 @@
+from unittest.mock import AsyncMock, Mock, patch
+
 import pytest
+from aioesphomeapi import (
+    APIClient,
+    APIVersion,
+    DeviceInfo,
+    ReconnectLogic,
+)
 from bleak_retry_connector import BleakSlotManager
 from bluetooth_adapters import BluetoothAdapters
 from habluetooth import (
     BluetoothManager,
     set_manager,
 )
+from zeroconf import Zeroconf
 
 
 @pytest.fixture(scope="session", autouse=True)
@@ -12,3 +21,73 @@ def manager():
     slot_manager = BleakSlotManager()
     bluetooth_adapters = BluetoothAdapters()
     set_manager(BluetoothManager(bluetooth_adapters, slot_manager))
+
+
+@pytest.fixture
+def mock_device_info() -> DeviceInfo:
+    """Return the default mocked device info."""
+    return DeviceInfo(
+        uses_password=False,
+        name="test",
+        legacy_bluetooth_proxy_version=0,
+        # ESPHome mac addresses are UPPER case
+        mac_address="11:22:33:44:55:AA",
+        esphome_version="1.0.0",
+    )
+
+
+class BaseMockReconnectLogic(ReconnectLogic):
+    """Mock ReconnectLogic."""
+
+    def stop_callback(self) -> None:
+        """Stop the reconnect logic."""
+        # For the purposes of testing, we don't want to wait
+        # for the reconnect logic to finish trying to connect
+        self._cancel_connect("forced disconnect from test")
+        self._is_stopped = True
+
+    async def stop(self) -> None:
+        """Stop the reconnect logic."""
+        self.stop_callback()
+
+
+@pytest.fixture
+def mock_client(mock_device_info: DeviceInfo) -> APIClient:
+    """Mock APIClient."""
+    mock_client = Mock(spec=APIClient)
+
+    def mock_constructor(
+        address: str,
+        port: int,
+        password: str | None,
+        *,
+        client_info: str = "aioesphomeapi",
+        keepalive: float = 15.0,
+        zeroconf_instance: Zeroconf = None,
+        noise_psk: str | None = None,
+        expected_name: str | None = None,
+    ) -> APIClient:
+        """Fake the client constructor."""
+        mock_client.host = address
+        mock_client.port = port
+        mock_client.password = password
+        mock_client.zeroconf_instance = zeroconf_instance
+        mock_client.noise_psk = noise_psk
+        return mock_client
+
+    mock_client.side_effect = mock_constructor
+    mock_client.device_info = AsyncMock(return_value=mock_device_info)
+    mock_client.connect = AsyncMock()
+    mock_client.disconnect = AsyncMock()
+    mock_client.list_entities_services = AsyncMock(return_value=([], []))
+    mock_client.address = "127.0.0.1"
+    mock_client.api_version = APIVersion(99, 99)
+
+    with (
+        patch(
+            "aioesphomeapi.ReconnectLogic",
+            BaseMockReconnectLogic,
+        ),
+        patch("aioesphomeapi.APIClient", mock_client),
+    ):
+        yield mock_client