test: add first unit test for VAD agent

Mocking audio input probabilities, checking whether it publishes audio data on the output socket.

ref: N25B-213

test/unit/conftest.py

@@ -0,0 +1,37 @@
+import sys
+from unittest.mock import MagicMock
+
+import sys
+from unittest.mock import MagicMock
+
+def pytest_configure(config):
+    """
+    This hook runs at the start of the pytest session, before any tests are
+    collected. It mocks heavy or unavailable modules to prevent ImportErrors.
+    """
+    # --- Mock spade and spade-bdi ---
+    mock_spade = MagicMock()
+    mock_spade.agent = MagicMock()
+    mock_spade.behaviour = MagicMock()
+    mock_spade_bdi = MagicMock()
+    mock_spade_bdi.bdi = MagicMock()
+
+    mock_spade.agent.Message = MagicMock()
+    mock_spade.behaviour.CyclicBehaviour = type('CyclicBehaviour', (object,), {})
+    mock_spade_bdi.bdi.BDIAgent = type('BDIAgent', (object,), {})
+
+    sys.modules['spade'] = mock_spade
+    sys.modules['spade.agent'] = mock_spade.agent
+    sys.modules['spade.behaviour'] = mock_spade.behaviour
+    sys.modules['spade_bdi'] = mock_spade_bdi
+    sys.modules['spade_bdi.bdi'] = mock_spade_bdi.bdi
+
+    # --- Mock the config module to prevent Pydantic ImportError ---
+    mock_config_module = MagicMock()
+    
+    # The code under test does `from ... import settings`, so our mock module
+    # must have a `settings` attribute. We'll make it a MagicMock so we can
+    # configure it later in our tests using mocker.patch.
+    mock_config_module.settings = MagicMock()
+    
+    sys.modules['control_backend.core.config'] = mock_config_module