Hi,
To know whether the module works in odoo community, odoo enterprise or in odoo sh, we have test it in all these versions and see. Once you tested the module in all the above, you can specify in your index file of the module that it has been tested and will work across all the odoo versions. By Doing this the one looks to buy the module will get the idea about whether it will work or not.
To test it in enterprise, either you need to get the enterprise code in your hand, or you have to share your module to anyone having enterprise code and ask them to test. Normally odoo partners and developers who works for them will be having the enterprise code. If you like to get it, you can get license from odoo and buy it.
To test it in Odoo.sh you have to get a project in odoo.sh, either you can get it buy paying for it, or ask some one who is having access to test and see.
Thanks