After reading this article you will know:
What a DTAP-street is
How you can implement a DTAP-street with sandboxes
The acronym DTAP is short for Development, Testing, Acceptance, and Production. Expressing a phased approach of software testing and deployment. More information about DTAP-streets can be found here.
DTAP with sandboxes
You can create sandboxes of sandboxes. This allows you to have multiple layers in which you can let other parties test new features. Each sandbox has its own users and data. You can merge the changes from sandbox to sandbox, one at a time. Production would be your application itself. Acceptance would be your first sandbox. Testing would be the sandbox of your first sandbox. Development would be the sandbox of the previous sandbox.
Read more about sandboxes here.