Dev 3.x flat package (#961)

* Move packages

* Added changelog

* Update examples/echo_bot.py

Co-authored-by: Oleg A. <t0rr@mail.ru>

* Rename `handler` -> `handlers`

* Update __init__.py

Co-authored-by: Oleg A. <t0rr@mail.ru>

tests/test_handler/test_message.py

@@ -0,0 +1,65 @@
+import datetime
+from typing import Any
+
+import pytest
+
+from aiogram.filters import CommandObject
+from aiogram.handlers import MessageHandler, MessageHandlerCommandMixin
+from aiogram.types import Chat, Message, User
+
+pytestmark = pytest.mark.asyncio
+
+
+class MyHandler(MessageHandler):
+    async def handle(self) -> Any:
+        return self.event.text
+
+
+class TestClassBasedMessageHandler:
+    async def test_message_handler(self):
+        event = Message(
+            message_id=42,
+            date=datetime.datetime.now(),
+            text="test",
+            chat=Chat(id=42, type="private"),
+            from_user=User(id=42, is_bot=False, first_name="Test"),
+        )
+        handler = MyHandler(event=event)
+
+        assert handler.from_user == event.from_user
+        assert handler.chat == event.chat
+
+
+class HandlerWithCommand(MessageHandlerCommandMixin, MessageHandler):
+    async def handle(self) -> Any:
+        return self.command
+
+
+class TestBaseMessageHandlerCommandMixin:
+    def test_command_accessible(self):
+        handler = HandlerWithCommand(
+            Message(
+                message_id=42,
+                date=datetime.datetime.now(),
+                text="/test args",
+                chat=Chat(id=42, type="private"),
+                from_user=User(id=42, is_bot=False, first_name="Test"),
+            ),
+            command=CommandObject(prefix="/", command="command", args="args"),
+        )
+
+        assert isinstance(handler.command, CommandObject)
+        assert handler.command.command == "command"
+
+    def test_command_not_presented(self):
+        handler = HandlerWithCommand(
+            Message(
+                message_id=42,
+                date=datetime.datetime.now(),
+                text="test",
+                chat=Chat(id=42, type="private"),
+                from_user=User(id=42, is_bot=False, first_name="Test"),
+            )
+        )
+
+        assert handler.command is None