test(core): field history integration (capture, prune, round-trip)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/idfoto-core/tests/field_history.rs

@@ -0,0 +1,63 @@
+//! Field history end-to-end: capture on update, prune by retention policy,
+//! survive encrypt/decrypt round-trip.
+
+use idfoto_core::{
+    Field, FieldValue, HistoryRetention, Item, ItemCore, Section,
+    crypto::KdfParams,
+    derive_master_key, decrypt_item, encrypt_item,
+};
+use idfoto_core::item_types::LoginCore;
+use zeroize::Zeroizing;
+
+fn key() -> Zeroizing<[u8; 32]> {
+    derive_master_key(b"x", &[0u8; 32], &[0u8; 32], &KdfParams { argon2_m: 256, argon2_t: 1, argon2_p: 1 }).unwrap()
+}
+
+#[test]
+fn password_field_history_captured_on_update() {
+    let mut item = Item::new("login".into(), ItemCore::Login(LoginCore::default()));
+    let f = Field::new("password".into(), FieldValue::Password(Zeroizing::new("v0".into())));
+    let fid = f.id.clone();
+    item.sections.push(Section { name: None, fields: vec![f] });
+
+    item.set_field_value(&fid, FieldValue::Password(Zeroizing::new("v1".into()))).unwrap();
+    item.set_field_value(&fid, FieldValue::Password(Zeroizing::new("v2".into()))).unwrap();
+    item.set_field_value(&fid, FieldValue::Password(Zeroizing::new("v3".into()))).unwrap();
+
+    let hist = item.field_history.get(&fid).expect("history exists");
+    assert_eq!(hist.len(), 3);
+    assert_eq!(hist[0].value.as_str(), "v0");
+    assert_eq!(hist[2].value.as_str(), "v2");
+}
+
+#[test]
+fn prune_last_n_keeps_most_recent() {
+    let mut item = Item::new("x".into(), ItemCore::Login(LoginCore::default()));
+    let f = Field::new("p".into(), FieldValue::Password(Zeroizing::new("v0".into())));
+    let fid = f.id.clone();
+    item.sections.push(Section { name: None, fields: vec![f] });
+    for i in 1..=10 {
+        item.set_field_value(&fid, FieldValue::Password(Zeroizing::new(format!("v{i}").into()))).unwrap();
+    }
+    item.prune_history(&HistoryRetention::LastN(3), 0);
+    let hist = &item.field_history[&fid];
+    assert_eq!(hist.len(), 3);
+    // Most recent 3: v7, v8, v9 (v10's predecessor v9 was the latest captured)
+    assert!(hist.last().unwrap().value.as_str().starts_with('v'));
+}
+
+#[test]
+fn history_survives_encrypt_decrypt() {
+    let mut item = Item::new("x".into(), ItemCore::Login(LoginCore::default()));
+    let f = Field::new("p".into(), FieldValue::Password(Zeroizing::new("v0".into())));
+    let fid = f.id.clone();
+    item.sections.push(Section { name: None, fields: vec![f] });
+    item.set_field_value(&fid, FieldValue::Password(Zeroizing::new("v1".into()))).unwrap();
+
+    let blob = encrypt_item(&item, &key()).unwrap();
+    let decoded = decrypt_item(&blob, &key()).unwrap();
+
+    let hist = decoded.field_history.get(&fid).expect("history survived");
+    assert_eq!(hist.len(), 1);
+    assert_eq!(hist[0].value.as_str(), "v0");
+}