Revert "Delete BuilderMockV0"

This is a combination of 3 commits:
* Revertion of commit b39a6833392ce44ca9d8b6e495e621c94208d049.
* Revertion of commit 61aea8db3d26d3ad02433ce344ed92037c738360.
* Revertion of commit 5f666aef668d8de1ae402491ce40e0a69563de80.