✅ add test cases

tests/plugins/param/param_event.py

@@ -0,0 +1,22 @@
+from nonebot.adapters import Event, Message
+from nonebot.params import EventToMe, EventType, EventMessage, EventPlainText
+
+
+async def event(e: Event) -> Event:
+    return e
+
+
+async def event_type(t: str = EventType()) -> str:
+    return t
+
+
+async def event_message(msg: Message = EventMessage()) -> Message:
+    return msg
+
+
+async def event_plain_text(text: str = EventPlainText()) -> str:
+    return text
+
+
+async def event_to_me(to_me: bool = EventToMe()) -> bool:
+    return to_me