Parsed test spec with 2 sessions

starting permutation: r1 r2 w1 w2 c1 c2
step r1: SELECT * FROM test WHERE i = 42;
i
-
(0 rows)

step r2: SELECT * FROM test WHERE i = 42;
i
-
(0 rows)

step w1: INSERT INTO test VALUES (42);
step w2: INSERT INTO test VALUES (42); <waiting ...>
step c1: COMMIT;
step w2: <... completed>
ERROR:  could not serialize access due to read/write dependencies among transactions
step c2: COMMIT;

starting permutation: r1 w1 c1 r2 w2 c2
step r1: SELECT * FROM test WHERE i = 42;
i
-
(0 rows)

step w1: INSERT INTO test VALUES (42);
step c1: COMMIT;
step r2: SELECT * FROM test WHERE i = 42;
 i
--
42
(1 row)

step w2: INSERT INTO test VALUES (42);
ERROR:  duplicate key value violates unique constraint "test_pkey"
step c2: COMMIT;