Though this is not applicable to Indian Commodities exchange and for products such as Urad, the prices of crude, gold , silver , soybeans and other popularly traded commodities are more or less same across the world ( or at least have a high correlation) and traders with longer time frames such as weeks would find this testing software extremely useful.
This is a software company founded by one of the original turtles ( Curtis Faith ) to develop and back test trading systems including commodities and Forex.
It is somewhat expensive ( one time fees of 2000 to 3000$ + monthly data feed price) , but as they say, you get what you pay for.
http://www.tradingblox.com/tradingblox/editionmatrix.htm
Adding this as well:
Trading commodities in the international markets is easy with InteractiveBrokers, you can choose to trade in a liquid commodities exchange and will actually end up paying less in commissions and slippages. There are mini contracts available for Crude, Gold, Soybeans , Corn etc as well.