Package storetest is the contract suite for pkg/store implementations
(decision 0015). Every backend (inmem, SQLite in memory and on disk,
PostgreSQL) runs Run with a factory that returns a fresh, empty store, so
one set of expectations defines the behaviour of all of them.
LongText returns n characters of random text, the same on every call. Half
the characters are two or three bytes of UTF-8 and each is one UTF-16 code
unit; all sort above "!" and none is an AQL wildcard.