test argument parser

tests/test_cli.py

@@ -0,0 +1,27 @@
+import unittest.mock
+
+import pytest
+
+import switchbot_mqtt
+
+
+@pytest.mark.parametrize(
+    ("argv", "expected_mqtt_host", "expected_mqtt_port"),
+    [
+        (["", "--mqtt-host", "mqtt-broker.local"], "mqtt-broker.local", 1883),
+        (
+            ["", "--mqtt-host", "mqtt-broker.local", "--mqtt-port", "8883"],
+            "mqtt-broker.local",
+            8883,
+        ),
+    ],
+)
+def test__main(argv, expected_mqtt_host, expected_mqtt_port):
+    with unittest.mock.patch("switchbot_mqtt._run") as run_mock, unittest.mock.patch(
+        "sys.argv", argv
+    ):
+        # pylint: disable=protected-access
+        switchbot_mqtt._main()
+    run_mock.assert_called_once_with(
+        mqtt_host=expected_mqtt_host, mqtt_port=expected_mqtt_port,
+    )