ensure agent name is unique, add some docs (#26)

tests/test_runtime.py

@@ -0,0 +1,32 @@
+from typing import Any, Sequence
+import pytest
+
+from agnext.application_components.single_threaded_agent_runtime import SingleThreadedAgentRuntime
+from agnext.core.agent_runtime import AgentRuntime
+from agnext.core.base_agent import BaseAgent
+from agnext.core.cancellation_token import CancellationToken
+
+class NoopAgent(BaseAgent):
+    def __init__(self, name: str, router: AgentRuntime) -> None:
+        super().__init__(name, router)
+
+    @property
+    def subscriptions(self) -> Sequence[type]:
+        return []
+
+    async def on_message(self, message: Any, cancellation_token: CancellationToken) -> Any:
+        raise NotImplementedError
+
+
+@pytest.mark.asyncio
+async def test_agent_names_must_be_unique() -> None:
+    router = SingleThreadedAgentRuntime()
+
+    _agent1 = NoopAgent("name1", router)
+
+    with pytest.raises(ValueError):
+        _agent1_again = NoopAgent("name1", router)
+
+    _agent3 = NoopAgent("name3", router)
+
+