We should add a set of multi-version tests that do the following:

• Build an index build on master, run validate() using 4.2. Test the combination of the following index types:
  • KeyString v0 ("v: 1" index)
  • KeyString v1  ("v: 2" index)
  • Non-unique
  • Unique
• Build an index on 4.2, and run validate() on master. This should be done with the same coverage as above
• This will need to be done for all index types (7), on data that is valid and representative of each index type