SharePoint Dragons

Not really easy to do. MS guidelines currently seem to recommend creating a local SharePoint environment that mimicks the structure you have online.

One option that is available for setting up a test environment is to become a MS partner for free (see https://partners.microsoft.com/partnerprogram/PartnerMembershipCenter.aspx ) and register for a free Office 365 subscription you could use as a test environment. Also check:

http://msdn.microsoft.com/en-us/library/hh147180.aspx#odc_sp14_ta_SPOnlineDevGuide_SetupDevEnvironment

This basically says: build sandboxed solutions in a local SharePoint env and test them there, because SPOL won’t let you do that.

Finally, check this: http://www.microsoft.com/download/en/details.aspx?id=17069