[pcf8574] Add reset option to preserve outputs across MCU reboots (#20589)

Co-authored-by: J. Nick Koston <nick@home-assistant.io>

tests/unit_tests/components/test_pcf8574.py

@@ -0,0 +1,35 @@
+"""PCF8574 reset configuration and code generation."""
+
+from unittest.mock import AsyncMock, Mock, patch
+
+import pytest
+
+from esphome.components import pcf8574
+from esphome.const import CONF_ID, CONF_RESET
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "options, expected",
+    [
+        ({}, True),
+        ({"reset": True}, True),
+        ({"reset": False}, False),
+    ],
+)
+async def test_reset_configuration(options: dict, expected: bool) -> None:
+    config = pcf8574.CONFIG_SCHEMA({CONF_ID: "hub", **options})
+    assert config[CONF_RESET] is expected
+    var = Mock()
+    with (
+        patch.object(pcf8574.cg, "new_Pvariable", return_value=var),
+        patch.object(pcf8574.cg, "register_component", new_callable=AsyncMock),
+        patch.object(pcf8574.i2c, "register_i2c_device", new_callable=AsyncMock),
+        patch.object(pcf8574.cg, "add"),
+    ):
+        await pcf8574.to_code(config)
+
+    if expected:
+        var.set_reset.assert_not_called()
+    else:
+        var.set_reset.assert_called_once_with(False)