Tests:

_hasa and _hash
  * Simple but also prove that death is done correctly
_find_raw
  * Autovivification
  * Scans lists and hashes correctly
  * Propagates unexpected death
_find
  * Scans all stashes
  * Proper death includes the property sought
CONFIG
  * Applies defaults
  * Handles lists in scalar/void
SECRET
  * not written yet
exists/true
  * Recycle CONFIG's default test for existence/truth
get
  * Don't bother
set
  * Test that %volatile is updated
append/prepend/replace
  * Test that @stack is changed
volatile/stack/default/stash
  * Correct return values
import
  * Check @EXPORT, @ISA and &import
  * Check that SECRET is the same but CONFIG has a unique coderef
  * Verify that the re-exported functions modify/access the correct variables

IO:

Figure out a sane and consistent way to load and deserialise files
with minimal magic or mental load on the user & developer.