diff --git a/src/sync_logic.rs b/src/sync_logic.rs
index f2a0e2b..57011b2 100644
--- a/src/sync_logic.rs
+++ b/src/sync_logic.rs
@@ -135,3 +135,72 @@ impl LtcState {
         &self.last_match_status
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use chrono::{Local, Utc};
+
+    fn get_test_frame(status: &str, h: u32, m: u32, s: u32) -> LtcFrame {
+        LtcFrame {
+            status: status.to_string(),
+            hours: h,
+            minutes: m,
+            seconds: s,
+            frames: 0,
+            frame_rate: 25.0,
+            timestamp: Utc::now(),
+        }
+    }
+
+    #[test]
+    fn test_ltc_frame_matches_system_time() {
+        let now = Local::now();
+        let frame = get_test_frame("LOCK", now.hour(), now.minute(), now.second());
+        assert!(frame.matches_system_time());
+    }
+
+    #[test]
+    fn test_ltc_frame_does_not_match_system_time() {
+        let now = Local::now();
+        // Create a time that is one hour ahead, wrapping around 23:00
+        let different_hour = (now.hour() + 1) % 24;
+        let frame = get_test_frame("LOCK", different_hour, now.minute(), now.second());
+        assert!(!frame.matches_system_time());
+    }
+
+    #[test]
+    fn test_ltc_state_update_lock() {
+        let mut state = LtcState::new();
+        let frame = get_test_frame("LOCK", 10, 20, 30);
+        state.update(frame);
+        assert_eq!(state.lock_count, 1);
+        assert_eq!(state.free_count, 0);
+        assert!(state.latest.is_some());
+    }
+
+    #[test]
+    fn test_ltc_state_update_free() {
+        let mut state = LtcState::new();
+        state.record_offset(100);
+        assert!(!state.offset_history.is_empty());
+
+        let frame = get_test_frame("FREE", 10, 20, 30);
+        state.update(frame);
+        assert_eq!(state.lock_count, 0);
+        assert_eq!(state.free_count, 1);
+        assert!(state.offset_history.is_empty()); // Offsets should be cleared
+        assert_eq!(state.last_match_status, "UNKNOWN");
+    }
+
+    #[test]
+    fn test_offset_history_management() {
+        let mut state = LtcState::new();
+        for i in 0..25 {
+            state.record_offset(i);
+        }
+        assert_eq!(state.offset_history.len(), 20);
+        assert_eq!(*state.offset_history.front().unwrap(), 5); // 0-4 are pushed out
+        assert_eq!(*state.offset_history.back().unwrap(), 24);
+    }
+}