As Salesforce.com gets ready to introduce its AppExchange on-demand application marketplace in the next several weeks, it's adding a related piece of its on-demand application puzzle with a service for testing the apps customers pick up on the exchange, as well as those they build themselves.

The new service, called Sandbox, is essentially an on-demand app-testing environment that provides customers with mirrored replicas of their Salesforce deployments so they can see how new and customized apps run before pushing them into production. The service will enable subscribers to replicate their entire application deployments, along with all of their live data, with a click of a button.

Sandbox was conceived over the past couple of months since AppExchange was first announced, the result of customer demand for some kind of parallel environment that would allow them to kick the tires of the applications they add by testing them against real data. The assumption is that the availability of a variety of new applications via the AppExchange will result in many Salesforce customers expanding their deployments with new capabilities. Sandbox is a way to increase AppExchange adoption by offering a layer of protection against potentially buggy apps by providing a glimpse at how they perform under production strain.

But Salesforce is aware that some customers may want to simplify things. "Some customers don't want to deal with information during testing," says Phill Robinson, executive VP of marketing. "It can be cumbersome to test customizations against a massive data set." For that reason, Salesforce is making the Sandbox available in two pricing options: A full-blown testing environment, with all production data, will run $25 a month per user, while companies that don't want to replicate their data can subscribe for $18 a month per user.

Sandbox and AppExchange both will be available by Jan. 31, with Sandbox offered only to customers of Salesforce's enterprise edition.