+# Convenience
+# A regexp to match 5, 35 and 40 hexdigits
+_x05='[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'
+_x35="$_x05$_x05$_x05$_x05$_x05$_x05$_x05"
+_x40="$_x35$_x05"
+
+test_oid_init
+
+ZERO_OID=$(test_oid zero)
+OID_REGEX=$(echo $ZERO_OID | sed -e 's/0/[0-9a-f]/g')
+EMPTY_TREE=$(test_oid empty_tree)
+EMPTY_BLOB=$(test_oid empty_blob)
+_z40=$ZERO_OID
+