add test

core/node/node_sync/src/fetcher.rs

@@ -201,3 +201,35 @@ impl IoCursorExt for IoCursor {
         new_actions
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use zksync_dal::{ConnectionPool, Core, CoreDal};
+    use zksync_node_genesis::{insert_genesis_batch, GenesisParams};
+    use zksync_state_keeper::io::IoCursor;
+    use zksync_types::{block::UnsealedL1BatchHeader, L1BatchNumber};
+
+    use crate::fetcher::IoCursorExt;
+
+    #[tokio::test]
+    async fn io_cursor_recognizes_empty_unsealed_batch() -> anyhow::Result<()> {
+        let pool = ConnectionPool::<Core>::test_pool().await;
+        let mut conn = pool.connection().await.unwrap();
+        insert_genesis_batch(&mut conn, &GenesisParams::mock())
+            .await
+            .unwrap();
+        conn.blocks_dal()
+            .insert_l1_batch(UnsealedL1BatchHeader {
+                number: L1BatchNumber(1),
+                timestamp: 1,
+                protocol_version: None,
+                fee_address: Default::default(),
+                fee_input: Default::default(),
+            })
+            .await?;
+
+        let io_cursor = IoCursor::for_fetcher(&mut conn).await?;
+        assert_eq!(io_cursor.l1_batch, L1BatchNumber(1));
+        Ok(())
+    }
+}