test: complete VAD unit and integration tests

Including an integration test with real voice audio.

ref: N25B-213

test/unit/agents/test_vad_socket_poller.py

@@ -0,0 +1,46 @@
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+import zmq
+
+from control_backend.agents.vad_agent import SocketPoller
+
+
+@pytest.fixture
+def socket():
+    return AsyncMock()
+
+
+@pytest.mark.asyncio
+async def test_socket_poller_with_data(socket, mocker):
+    socket_data = b"test"
+    socket.recv.return_value = socket_data
+
+    mock_poller: MagicMock = mocker.patch("control_backend.agents.vad_agent.zmq.Poller")
+    mock_poller.return_value.poll.return_value = [(socket, zmq.POLLIN)]
+
+    poller = SocketPoller(socket)
+    # Calling `poll` twice to be able to check that the poller is reused
+    await poller.poll()
+    data = await poller.poll()
+
+    assert data == socket_data
+
+    # Ensure that the poller was reused
+    mock_poller.assert_called_once_with()
+    mock_poller.return_value.register.assert_called_once_with(socket, zmq.POLLIN)
+
+    assert socket.recv.call_count == 2
+
+
+@pytest.mark.asyncio
+async def test_socket_poller_no_data(socket, mocker):
+    mock_poller: MagicMock = mocker.patch("control_backend.agents.vad_agent.zmq.Poller")
+    mock_poller.return_value.poll.return_value = []
+
+    poller = SocketPoller(socket)
+    data = await poller.poll()
+
+    assert data is None
+
+    socket.recv.assert_not_called()