Pin theme snapshot defaults and offline preview behavior

crates/ferese-config/tests/theme_wire.rs

@@ -0,0 +1,52 @@
+use ferese_config::theme::Snapshot;
+use serde_json::{Value, json};
+
+fn fixture() -> Value {
+    serde_json::from_str(include_str!("fixtures/theme-v2.json")).unwrap()
+}
+
+#[test]
+fn default_snapshot_preserves_wire_values_and_environment_wallpaper() {
+    let mut snapshot = Snapshot::default();
+    let wallpaper = Some(ferese_config::default_wallpaper().into());
+    assert_eq!(snapshot.theme.tokens.background.path, wallpaper);
+    assert_eq!(snapshot.presented.tokens.background.path, wallpaper);
+    snapshot.theme.tokens.background.path = Some("<wallpaper>".into());
+    snapshot.presented.tokens.background.path = Some("<wallpaper>".into());
+    assert_eq!(serde_json::to_value(snapshot).unwrap(), fixture());
+}
+
+#[test]
+fn older_snapshots_supply_catalog_but_explicit_empty_catalog_stays_empty() {
+    let mut value = fixture();
+    value.as_object_mut().unwrap().remove("families");
+    value.as_object_mut().unwrap().remove("fallback_note");
+    let snapshot: Snapshot = serde_json::from_value(value.clone()).unwrap();
+    assert_eq!(snapshot.families, ferese_config::families::builtins());
+    assert_eq!(snapshot.fallback_note, None);
+    value["families"] = json!([]);
+    assert!(
+        serde_json::from_value::<Snapshot>(value.clone())
+            .unwrap()
+            .families
+            .is_empty()
+    );
+    value["families"] = Value::Null;
+    assert!(serde_json::from_value::<Snapshot>(value).is_err());
+}
+
+#[test]
+fn offline_preview_resolves_without_changing_published_values() {
+    let before = Snapshot::default();
+    let document = ferese_config::Document::parse("theme { mode \"light\"; family \"gruvbox\"; }\n").unwrap();
+    let candidate = ferese_config::theme::resolve(
+        &document,
+        std::path::Path::new("/unused"),
+        "2026-10-02T12:00:00Z".parse().unwrap(),
+        |_| panic!("built-in preview must not read theme files"),
+    )
+    .unwrap();
+    assert_eq!(candidate.theme.appearance, ferese_config::theme::Appearance::Light);
+    assert_eq!(candidate.theme.tokens.colors.surface_base, "#FBF1C7");
+    assert_eq!(before, Snapshot::default());
+}