test: cover resolve_library_param and per-library ExifDao filter

Adds 9 unit tests around the library plumbing:
- resolve_library_param branches (absent, empty/whitespace, numeric id,
  name, unknown id, unknown name)
- Library::resolve symmetry with strip_root
- ExifDao::get_all_with_date_taken in union and scoped modes

Introduces SqliteExifDao::from_connection test constructor mirroring the
existing preview_dao pattern so DAO tests can drive an in-memory SQLite.

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

src/database/mod.rs

@@ -403,6 +403,13 @@ impl SqliteExifDao {
             connection: Arc::new(Mutex::new(connect())),
         }
     }
+
+    #[cfg(test)]
+    pub fn from_connection(conn: SqliteConnection) -> Self {
+        SqliteExifDao {
+            connection: Arc::new(Mutex::new(conn)),
+        }
+    }
 }
 
 impl ExifDao for SqliteExifDao {
@@ -927,3 +934,92 @@ impl ExifDao for SqliteExifDao {
         .map_err(|_| DbError::new(DbErrorKind::QueryError))
     }
 }
+
+#[cfg(test)]
+mod exif_dao_tests {
+    use super::*;
+    use crate::database::models::InsertLibrary;
+    use crate::database::test::in_memory_db_connection;
+
+    fn ctx() -> opentelemetry::Context {
+        opentelemetry::Context::new()
+    }
+
+    fn insert_row(dao: &mut SqliteExifDao, lib_id: i32, rel: &str, date: Option<i64>) {
+        dao.store_exif(
+            &ctx(),
+            InsertImageExif {
+                library_id: lib_id,
+                file_path: rel.to_string(),
+                camera_make: None,
+                camera_model: None,
+                lens_model: None,
+                width: None,
+                height: None,
+                orientation: None,
+                gps_latitude: None,
+                gps_longitude: None,
+                gps_altitude: None,
+                focal_length: None,
+                aperture: None,
+                shutter_speed: None,
+                iso: None,
+                date_taken: date,
+                created_time: 0,
+                last_modified: 0,
+                content_hash: None,
+                size_bytes: None,
+            },
+        )
+        .expect("insert exif row");
+    }
+
+    fn setup_two_libraries() -> SqliteExifDao {
+        let mut conn = in_memory_db_connection();
+        // Migration seeds library id=1 with a placeholder root; add id=2.
+        diesel::insert_into(schema::libraries::table)
+            .values(InsertLibrary {
+                name: "archive",
+                root_path: "/tmp/archive",
+                created_at: 0,
+            })
+            .execute(&mut conn)
+            .expect("seed second library");
+        SqliteExifDao::from_connection(conn)
+    }
+
+    #[test]
+    fn get_all_with_date_taken_union_returns_all_libraries() {
+        let mut dao = setup_two_libraries();
+        insert_row(&mut dao, 1, "main/a.jpg", Some(100));
+        insert_row(&mut dao, 2, "archive/b.jpg", Some(200));
+        // Row without a date must be excluded even in union mode.
+        insert_row(&mut dao, 2, "archive/c.jpg", None);
+
+        let mut rows = dao.get_all_with_date_taken(&ctx(), None).unwrap();
+        rows.sort_by_key(|(_, ts)| *ts);
+        assert_eq!(
+            rows,
+            vec![
+                ("main/a.jpg".to_string(), 100),
+                ("archive/b.jpg".to_string(), 200),
+            ]
+        );
+    }
+
+    #[test]
+    fn get_all_with_date_taken_scopes_by_library_id() {
+        let mut dao = setup_two_libraries();
+        insert_row(&mut dao, 1, "main/a.jpg", Some(100));
+        insert_row(&mut dao, 2, "archive/b.jpg", Some(200));
+        insert_row(&mut dao, 2, "archive/c.jpg", Some(300));
+
+        let lib2 = dao.get_all_with_date_taken(&ctx(), Some(2)).unwrap();
+        let mut paths: Vec<String> = lib2.into_iter().map(|(p, _)| p).collect();
+        paths.sort();
+        assert_eq!(paths, vec!["archive/b.jpg", "archive/c.jpg"]);
+
+        let lib1 = dao.get_all_with_date_taken(&ctx(), Some(1)).unwrap();
+        assert_eq!(lib1, vec![("main/a.jpg".to_string(), 100)]);
+    }
+}