Maybe use all of this:

1) checkpoint

2) dbcc dropcleanbuffers

3) dbcc freeproccache

4) dbcc freesystemcache('all')

(The last one N4 probably is the same as N2 + N3).

Using tests for the whole TB database may be very time-consuming even when you have the whole DB available. This should be done after the first approach with reduced in size DB.