test config variable disk data round trip and validation

CMK-37088

Change-Id: Id7f3539b8bc9ce230a7bb2841c8bd30cd6a3318a

Author: MakeilaLun

tests/testlib/gui/common_fixtures.py

@@ -285,5 +285,9 @@ def patch_theme_context() -> Iterator[None]:
             "cmk.gui.theme.choices.theme_choices",
             return_value=[("modern-dark", "dark ut"), ("facelift", "light ut")],
         ),
+        patch(
+            "cmk.gui.wato._check_mk_configuration.theme_choices",
+            return_value=[("modern-dark", "dark ut"), ("facelift", "light ut")],
+        ),
     ):
         yield

tests/testlib/unit/BUILD

@@ -38,6 +38,7 @@ py_library(
         "//cmk/gui/watolib:config_infra",
         "//cmk/gui/watolib:password_store",
         "//packages/cmk-crash:crash",
+        "//tests/testlib:fake_site",
         "//tests/testlib:rest_api_client",
         "//tests/testlib/common:empty_config",
         "//tests/testlib/common:repo",