diff --git a/util/test-10.ndb b/util/test-10.ndb
new file mode 100644
index 0000000..844afda
--- /dev/null
+++ b/util/test-10.ndb
@@ -0,0 +1,10 @@
+Lib_Open 0
+DS_Open
+Index_List_Open 0-0
+DS_Value_Add 1-10 0
+DS_Value_Find 1-10
+Index_List_To_Tree 0-0
+DS_Value_Find 1-10
+DS_Check
+DS_Close
+Lib_Close
diff --git a/util/test-error.ndb b/util/test-error.ndb
new file mode 100644
index 0000000..81ed550
--- /dev/null
+++ b/util/test-error.ndb
@@ -0,0 +1,11 @@
+DS_Open
+Lib_Open 0
+DS_Open
+Index_List_Open 0-0
+DS_Value_Add 1-10 0
+Lib_Close
+Lib_Open 1
+DS_Open
+Index_List_Open 0-0
+DS_Value_Add 1-10 0
+Lib_Close