fontconfig: check warning in legacy default test

tests/modules/misc/fontconfig/default.nix

@@ -9,5 +9,5 @@
   fontconfig-extra-config-files = ./extra-config-files.nix;
   fontconfig-fonts = ./fonts.nix;
 
-  fontconfig-old-default-configFile-toggle = ./old-default-configFile-toggle.nix;
+  fontconfig-legacy-default-configFile-toggle = ./legacy-default-configFile-toggle.nix;
 }

tests/modules/misc/fontconfig/legacy-default-configFile-toggle.nix

@@ -0,0 +1,29 @@
+let
+  fcConfD = "home-files/.config/fontconfig/conf.d";
+in
+{
+  home.stateVersion = "26.05"; # <= 26.11
+
+  fonts.fontconfig = {
+    enable = true;
+    configFile.implicitly-disabled.text = "foo";
+  };
+
+  asserts.warning.expected = [
+    ''
+      The default value of `fonts.fontconfig.configFile.implicitly-disabled.enable` has changed from `false` to `true`.
+      You are currently using the legacy default (`false`) because `home.stateVersion` is less than "26.11".
+      To silence this warning and keep legacy behavior, set:
+        fonts.fontconfig.configFile.implicitly-disabled.enable = false;
+      To adopt the new default behavior, set:
+        fonts.fontconfig.configFile.implicitly-disabled.enable = true;
+    ''
+  ];
+
+  nmt.script = ''
+    assertFileExists ${fcConfD}/10-hm-fonts.conf
+    assertFileExists ${fcConfD}/52-hm-default-fonts.conf
+
+    assertPathNotExists ${fcConfD}/90-hm-implicitly-disabled.conf
+  '';
+}

tests/modules/misc/fontconfig/old-default-configFile-toggle.nix

@@ -1,18 +0,0 @@
-let
-  fcConfD = "home-files/.config/fontconfig/conf.d";
-in
-{
-  home.stateVersion = "26.05"; # <= 26.11
-
-  fonts.fontconfig = {
-    enable = true;
-    configFile.implicitly-disabled.text = "foo";
-  };
-
-  nmt.script = ''
-    assertFileExists ${fcConfD}/10-hm-fonts.conf
-    assertFileExists ${fcConfD}/52-hm-default-fonts.conf
-
-    assertPathNotExists ${fcConfD}/90-hm-implicitly-disabled.conf
-  '';
-}