zuuid: check for errors in constructor
zthread: Assert context creation
zthread: assert zstr_recv returns a string
zstr: assert message creation
zstr: assert zstr_recv returns a string
zsock: check creation in constructors
zsock: check zsys_vprintf returns a string
zsock: check zmsg_addmem succeeds
zsock: assert constructors succeed in test
zmsg: Use destructor when constructor fails
zmsg: Check creating zframe succeeds
zmsg: check allocating buffer for encoding succeeds
zlist: duplicate destructor and duplicator only when creating copy succeeds
zsys: Check zlist creation in init
zsys: Check for errors in curve check
zfile: Check for errors in constructor
zfile: Check constructor succeeds for computing digest
zfile: check constructors succeed in test
zring: Check zhash creation in insert
zrex: don't assert in constructor