diff --git a/tests/test_event.py b/tests/test_event.py
new file mode 100644
index 00000000..a5c0c2a2
--- /dev/null
+++ b/tests/test_event.py
@@ -0,0 +1,185 @@
+"""Event tests for ZHA."""
+
+from __future__ import annotations
+
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from zha.application.gateway import Gateway
+from zha.event import EventBase
+
+
+class EventGenerator(EventBase):
+    """Event generator for testing."""
+
+
+class Event:
+    """Event class for testing."""
+
+    event = "test"
+    event_type = "testing"
+
+
+def test_event_base_unsubs():
+    """Test event base class."""
+    event = EventGenerator()
+    assert not event._listeners
+    assert not event._golbal_listeners
+
+    callback = MagicMock()
+
+    unsub = event.on_event("test", callback)
+    assert event._listeners == {"test": [callback]}
+    unsub()
+    assert event._listeners == {"test": []}
+
+    unsub = event.on_all_events(callback)
+    assert event._golbal_listeners == [callback]
+    unsub()
+    assert not event._golbal_listeners
+
+    unsub = event.once("test", callback)
+    assert "test" in event._listeners
+    assert len(event._listeners["test"]) == 1
+    unsub()
+    assert event._listeners == {"test": []}
+
+
+def test_event_base_emit():
+    """Test event base class."""
+    event = EventGenerator()
+    assert not event._listeners
+    assert not event._golbal_listeners
+
+    callback = MagicMock()
+
+    event.once("test", callback)
+    event.emit("test")
+    assert callback.called
+
+    callback.reset_mock()
+    event.emit("test")
+    assert not callback.called
+
+    unsub = event.on_event("test", callback)
+    event.emit("test")
+    assert callback.called
+    unsub()
+
+    callback.reset_mock()
+    unsub = event.on_all_events(callback)
+    event.emit("test")
+    assert callback.called
+    unsub()
+
+    assert "test" in event._listeners
+    assert event._listeners == {"test": []}
+    assert not event._golbal_listeners
+
+
+def test_event_base_emit_data():
+    """Test event base class."""
+    event = EventGenerator()
+    assert not event._listeners
+    assert not event._golbal_listeners
+
+    callback = MagicMock()
+
+    event.once("test", callback)
+    event.emit("test", "data")
+    assert callback.called
+    assert callback.call_args[0] == ("data",)
+
+    callback.reset_mock()
+    event.emit("test", "data")
+    assert not callback.called
+
+    unsub = event.on_event("test", callback)
+    event.emit("test", "data")
+    assert callback.called
+    assert callback.call_args[0] == ("data",)
+    unsub()
+
+    callback.reset_mock()
+    unsub = event.on_all_events(callback)
+    event.emit("test", "data")
+    assert callback.called
+    assert callback.call_args[0] == ("data",)
+    unsub()
+
+    assert "test" in event._listeners
+    assert event._listeners == {"test": []}
+    assert not event._golbal_listeners
+
+
+async def test_event_base_emit_coro(zha_gateway: Gateway):
+    """Test event base class."""
+    event = EventGenerator()
+    assert not event._listeners
+    assert not event._golbal_listeners
+
+    callback = AsyncMock()
+
+    event.once("test", callback)
+    event.emit("test", "data")
+    await zha_gateway.async_block_till_done()
+    await zha_gateway.async_block_till_done()
+    assert callback.await_count == 1
+    assert callback.await_args[0] == ("data",)
+
+    callback.reset_mock()
+
+    unsub = event.on_event("test", callback)
+    event.emit("test", "data")
+    await zha_gateway.async_block_till_done()
+    await zha_gateway.async_block_till_done()
+    assert callback.await_count == 1
+    assert callback.await_args[0] == ("data",)
+    unsub()
+
+    callback.reset_mock()
+
+    unsub = event.on_all_events(callback)
+    event.emit("test", "data")
+    await zha_gateway.async_block_till_done()
+    await zha_gateway.async_block_till_done()
+    assert callback.await_count == 1
+    assert callback.await_args[0] == ("data",)
+    unsub()
+
+    test_event = Event()
+    event.on_event(test_event.event, event._handle_event_protocol)
+    event.handle_test = AsyncMock()
+
+    event.emit(test_event.event, test_event)
+    await zha_gateway.async_block_till_done()
+    await zha_gateway.async_block_till_done()
+
+    assert event.handle_test.await_count == 1
+    assert event.handle_test.await_args[0] == (test_event,)
+
+
+def test_handle_event_protocol():
+    """Test event base class."""
+
+    event_handler = EventGenerator()
+    event_handler.handle_test = MagicMock()
+    event_handler.on_event("test", event_handler._handle_event_protocol)
+
+    event = Event()
+    event_handler.emit(event.event, event)
+
+    assert event_handler.handle_test.called
+    assert event_handler.handle_test.call_args[0] == (event,)
+
+
+def test_handle_event_protocol_no_event(caplog: pytest.LogCaptureFixture):
+    """Test event base class."""
+
+    event_handler = EventGenerator()
+    event_handler.on_event("not_test", event_handler._handle_event_protocol)
+    event = Event()
+    event_handler.emit("not_test", event)
+
+    assert "Received unknown event:" in caplog.text
diff --git a/zha/event.py b/zha/event.py
index 143e6a48..80f1848b 100644
--- a/zha/event.py
+++ b/zha/event.py
@@ -50,31 +50,32 @@ def unsubscribe() -> None:
 
     def once(self, event_name: str, callback: Callable) -> Callable:
         """Listen for an event exactly once."""
+        if inspect.iscoroutinefunction(callback):
+
+            async def async_event_listener(data: dict) -> None:
+                unsub()
+                task = asyncio.create_task(callback(data))
+                self._event_tasks.append(task)
+                task.add_done_callback(self._event_tasks.remove)
+
+            unsub = self.on_event(event_name, async_event_listener)
+            return unsub
 
         def event_listener(data: dict) -> None:
             unsub()
             callback(data)
 
         unsub = self.on_event(event_name, event_listener)
-
         return unsub
 
     def emit(self, event_name: str, data=None) -> None:
         """Run all callbacks for an event."""
         for listener in [*self._listeners.get(event_name, []), *self._golbal_listeners]:
             if inspect.iscoroutinefunction(listener):
-                if data is None:
-                    task = asyncio.create_task(listener())
-                    self._event_tasks.append(task)
-                    task.add_done_callback(self._event_tasks.remove)
-                else:
-                    task = asyncio.create_task(listener(data))
-                    self._event_tasks.append(task)
-                    task.add_done_callback(self._event_tasks.remove)
-            elif data is None:
-                listener()
-            else:
-                listener(data)
+                task = asyncio.create_task(listener(data))
+                self._event_tasks.append(task)
+                task.add_done_callback(self._event_tasks.remove)
+            listener(data)
 
     def _handle_event_protocol(self, event) -> None:
         """Process an event based on event protocol."""