Parsed test spec with 2 sessions

starting permutation: rw1 rw2 c1 c2
step rw1: SELECT insert_unique(1, '1');
insert_unique
-------------
             
(1 row)

step rw2: SELECT insert_unique(1, '2'); <waiting ...>
step c1: COMMIT;
step rw2: <... completed>
ERROR:  could not serialize access due to read/write dependencies among transactions
step c2: COMMIT;