test: add unit tests for main and actuation receivers

Exhaustive test cases for both classes, with 100% coverage. Adds `mock` dependency. Tests for actuation receiver do not yet pass.

ref: N25B-168

test/unit/test_main_receiver.py

@@ -0,0 +1,79 @@
+import unittest
+
+import mock
+import zmq
+
+from robot_interface.endpoints.main_receiver import MainReceiver
+
+
+class TestMainReceiver(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.context = zmq.Context()
+
+    def test_handle_ping(self):
+        receiver = MainReceiver(self.context)
+        response = receiver.handle_message({"endpoint": "ping", "data": "pong"})
+
+        self.assertIn("endpoint", response)
+        self.assertEqual(response["endpoint"], "ping")
+        self.assertIn("data", response)
+        self.assertEqual(response["data"], "pong")
+
+    def test_handle_ping_none(self):
+        receiver = MainReceiver(self.context)
+        response = receiver.handle_message({"endpoint": "ping", "data": None})
+
+        self.assertIn("endpoint", response)
+        self.assertEqual(response["endpoint"], "ping")
+        self.assertIn("data", response)
+        self.assertEqual(response["data"], None)
+
+    @mock.patch("robot_interface.endpoints.main_receiver.state")
+    def test_handle_negotiate_ports(self, mock_state):
+        receiver = MainReceiver(self.context)
+        mock_state.sockets = [receiver]
+
+        response = receiver.handle_message({"endpoint": "negotiate/ports", "data": None})
+
+        self.assertIn("endpoint", response)
+        self.assertEqual(response["endpoint"], "negotiate/ports")
+        self.assertIn("data", response)
+        self.assertIsInstance(response["data"], list)
+        for port in response["data"]:
+            self.assertIn("id", port)
+            self.assertIsInstance(port["id"], str)
+            self.assertIn("port", port)
+            self.assertIsInstance(port["port"], int)
+            self.assertIn("bind", port)
+            self.assertIsInstance(port["bind"], bool)
+
+        self.assertTrue(any(port["id"] == "main" for port in response["data"]))
+
+    def test_handle_unimplemented_endpoint(self):
+        receiver = MainReceiver(self.context)
+        response = receiver.handle_message({
+            "endpoint": "some_endpoint_that_definitely_does_not_exist",
+            "data": None,
+        })
+
+        self.assertIn("endpoint", response)
+        self.assertEqual(response["endpoint"], "error")
+        self.assertIn("data", response)
+        self.assertIsInstance(response["data"], str)
+
+    def test_handle_unimplemented_negotiation_endpoint(self):
+        receiver = MainReceiver(self.context)
+        response = receiver.handle_message({
+            "endpoint": "negotiate/but_some_subpath_that_definitely_does_not_exist",
+            "data": None,
+        })
+
+        self.assertIn("endpoint", response)
+        self.assertEqual(response["endpoint"], "negotiate/error")
+        self.assertIn("data", response)
+        self.assertIsInstance(response["data"], str)
+
+
+if __name__ == "__main__":
+    unittest.main()