tx-pool: add unit tests for FinalizedBlockTracker update (#10078)

crates/transaction-pool/src/maintain.rs

@@ -742,4 +742,46 @@ mod tests {
 
         temp_dir.close().unwrap();
     }
+
+    #[test]
+    fn test_update_with_higher_finalized_block() {
+        let mut tracker = FinalizedBlockTracker::new(Some(10));
+        assert_eq!(tracker.update(Some(15)), Some(15));
+        assert_eq!(tracker.last_finalized_block, Some(15));
+    }
+
+    #[test]
+    fn test_update_with_lower_finalized_block() {
+        let mut tracker = FinalizedBlockTracker::new(Some(20));
+        assert_eq!(tracker.update(Some(15)), None);
+        assert_eq!(tracker.last_finalized_block, Some(15));
+    }
+
+    #[test]
+    fn test_update_with_equal_finalized_block() {
+        let mut tracker = FinalizedBlockTracker::new(Some(20));
+        assert_eq!(tracker.update(Some(20)), None);
+        assert_eq!(tracker.last_finalized_block, Some(20));
+    }
+
+    #[test]
+    fn test_update_with_no_last_finalized_block() {
+        let mut tracker = FinalizedBlockTracker::new(None);
+        assert_eq!(tracker.update(Some(10)), Some(10));
+        assert_eq!(tracker.last_finalized_block, Some(10));
+    }
+
+    #[test]
+    fn test_update_with_no_new_finalized_block() {
+        let mut tracker = FinalizedBlockTracker::new(Some(10));
+        assert_eq!(tracker.update(None), None);
+        assert_eq!(tracker.last_finalized_block, Some(10));
+    }
+
+    #[test]
+    fn test_update_with_no_finalized_blocks() {
+        let mut tracker = FinalizedBlockTracker::new(None);
+        assert_eq!(tracker.update(None), None);
+        assert_eq!(tracker.last_finalized_block, None);
+    }
 }