tool for testing add-on products before migrating them?

[Asen QUINTANA]

Hi to everyone,
I'm starting with the fantastic task of migrating my site from 2.1.2 to
2.5.3..and if I can to 3.0. I have a lot of customized archetypes and
scripts, and I'm not sure they are going to work, I wonder if a tool exists
to test code to be sure of compatibility?

I'm also using ExternalFile for saving docs outside my ZODB, but it's no
longer supported !!.Any suggestions about which product  I can use instead
of this ???
Thanks in advance

Asen Quintana