[wifi] Add DHCP lease cache (#17767)

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

tests/component_tests/wifi/test_lease_cache.py

@@ -0,0 +1,41 @@
+"""Tests for the lease_cache storage validation."""
+
+import pytest
+
+from esphome import config_validation as cv
+from esphome.components.esp32 import KEY_VARIANT
+from esphome.components.esp32.const import VARIANT_ESP32, VARIANT_ESP32C2
+from esphome.components.wifi import CONFIG_SCHEMA
+from esphome.const import PlatformFramework
+from tests.component_tests.types import SetCoreConfigCallable
+
+
+def _validate(lease_cache: dict) -> dict:
+    return CONFIG_SCHEMA(
+        {
+            "ssid": "net",
+            "password": "secret12",
+            "use_address": "test.local",
+            "lease_cache": lease_cache,
+        }
+    )
+
+
+def test_storage_defaults_to_rtc(set_core_config: SetCoreConfigCallable) -> None:
+    set_core_config(
+        PlatformFramework.ESP32_IDF, platform_data={KEY_VARIANT: VARIANT_ESP32}
+    )
+    config = _validate({"max_age": "12h"})
+    assert config["lease_cache"]["storage"] == "rtc"
+
+
+def test_no_rtc_variant_requires_flash(set_core_config: SetCoreConfigCallable) -> None:
+    """A variant without RTC memory must say storage: flash; the error points at that key."""
+    set_core_config(
+        PlatformFramework.ESP32_IDF, platform_data={KEY_VARIANT: VARIANT_ESP32C2}
+    )
+    with pytest.raises(cv.Invalid, match="no RTC memory") as exc:
+        _validate({"max_age": "12h"})
+    assert exc.value.path == ["lease_cache", "storage"]
+    config = _validate({"storage": "flash"})
+    assert config["lease_cache"]["storage"] == "flash"