Using random piece num may generate the exact same key or piecenum.
Instead use fixed piecenum and key.
Change-Id: I54b7bc1a6698149bf99608dd46501ea963cec084
Testing interfaces is slightly clearer when it's in the package needing
the database rather than each individual implementation.
Change-Id: I10334c214a205f7e510b939b4359a2214c4e060a