[ch423] Add CH423 I/O expander component (#13079)

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

tests/unit_tests/components/test_ch423.py

@@ -0,0 +1,58 @@
+"""Tests for ch423 component validation."""
+
+from unittest.mock import patch
+
+from esphome import config, yaml_util
+from esphome.core import CORE
+
+
+def test_ch423_mixed_gpio_modes_fails(tmp_path, capsys):
+    """Test that mixing input/output on GPIO pins 0-7 fails validation."""
+    test_file = tmp_path / "test.yaml"
+    test_file.write_text("""
+esphome:
+  name: test
+
+esp8266:
+  board: esp01_1m
+
+i2c:
+  sda: GPIO4
+  scl: GPIO5
+
+ch423:
+  - id: ch423_hub
+
+binary_sensor:
+  - platform: gpio
+    name: "CH423 Input 0"
+    pin:
+      ch423: ch423_hub
+      number: 0
+      mode: input
+
+switch:
+  - platform: gpio
+    name: "CH423 Output 1"
+    pin:
+      ch423: ch423_hub
+      number: 1
+      mode: output
+""")
+
+    parsed_yaml = yaml_util.load_yaml(test_file)
+
+    with (
+        patch.object(yaml_util, "load_yaml", return_value=parsed_yaml),
+        patch.object(CORE, "config_path", test_file),
+    ):
+        result = config.read_config({})
+
+    assert result is None, "Expected validation to fail with mixed GPIO modes"
+
+    # Check that the error message mentions the GPIO pin restriction
+    captured = capsys.readouterr()
+    assert (
+        "GPIO pins (0-7) must all be configured as input or all as output"
+        in captured.out
+    )