add FutureMoves::tests::prune_tree_test parents for children

src/logic/future_moves.rs

@@ -488,6 +488,11 @@ mod tests {
             Piece::Black,
             Some(0),
         ));
+
+        for i in futm.arena[0].children.clone() {
+            futm.arena[i].parent = Some(0);
+        }
+
         assert_eq!(futm.arena_len(), 5);
 
         futm.refocus_tree();