test: added tests and docstrings

ref: N25B-397

test/unit/test_main.py

@@ -55,6 +55,9 @@ class DummySender:
     def start(self):
         self.called = True
 
+    def start_face_detection(self):
+        self.called = True
+
     def close(self):
         pass
 
@@ -108,11 +111,13 @@ def patched_main_components(monkeypatch, fake_sockets, fake_poll):
     fake_act = FakeReceiver(act_sock)
     video_sender = DummySender()
     audio_sender = DummySender()
+    face_sender = DummySender()
 
     monkeypatch.setattr(main_mod, "MainReceiver", lambda ctx: fake_main)
     monkeypatch.setattr(main_mod, "ActuationReceiver", lambda ctx: fake_act)
     monkeypatch.setattr(main_mod, "VideoSender", lambda ctx: video_sender)
     monkeypatch.setattr(main_mod, "AudioSender", lambda ctx: audio_sender)
+    monkeypatch.setattr(main_mod, "FaceDetectionSender", lambda ctx: face_sender)
 
     # Register sockets for the fake poller
     fake_poll.registered = {main_sock: zmq.POLLIN, act_sock: zmq.POLLIN}