improve portability of test

src/test/res/ids.lua

@@ -1,5 +1,7 @@
 -- utility to give tables and functions uniform ids for testing
 ids = {}
+
+-- return unique id for the value, independent of object id
 function id(obj)
 	if not obj or type(obj) == 'number' or type(obj) == 'string' or type(obj) == 'boolean' then
 		return obj
@@ -12,3 +14,23 @@ function id(obj)
 	ids[obj] = type(obj)..'.'..tostring(#ids)
 	return ids[obj]
 end 
+
+-- return key-value pairs sorted by keys
+function spairs(unsorted)
+	local keys = {}
+	for k,v in pairs(unsorted) do
+		table.insert(keys,k)
+	end
+	table.sort(keys)
+	local lookup = {}
+	for i,k in ipairs(keys) do
+		lookup[k] = i;
+	end
+	local iterator = function(tbl,key)
+		local i = lookup[key]
+		local j,k = next(keys,i)
+		if not j then return nil end
+		return k,unsorted[k]
+	end
+	return iterator, table, nil
+end