Testing Using The Beta Tier
developers.facebook.com/blog/post/438
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
A long-standing but often forgotten tip for building on Platform is to test your app against our beta tier, which we push to every Sunday night. This gives you around 48 hours to confirm that your app will not have any issues with the code (features, updates, bug fixes, etc.) that we will be pushing to the full web tier on Tuesday afternoon.