Parsed test spec with 2 sessions

starting permutation: s1a s2a s2b s1b s2c
step s1a: SELECT * FROM foo FOR SHARE NOWAIT;
id|data
--+----
 1|x   
(1 row)

step s2a: SELECT * FROM foo FOR SHARE NOWAIT;
id|data
--+----
 1|x   
(1 row)

step s2b: SELECT * FROM foo FOR UPDATE NOWAIT;
ERROR:  could not obtain lock on row in relation "foo"
step s1b: COMMIT;
step s2c: COMMIT;

starting permutation: s2a s1a s2b s1b s2c
step s2a: SELECT * FROM foo FOR SHARE NOWAIT;
id|data
--+----
 1|x   
(1 row)

step s1a: SELECT * FROM foo FOR SHARE NOWAIT;
id|data
--+----
 1|x   
(1 row)

step s2b: SELECT * FROM foo FOR UPDATE NOWAIT;
ERROR:  could not obtain lock on row in relation "foo"
step s1b: COMMIT;
step s2c: COMMIT;

starting permutation: s2a s2b s1a s1b s2c
step s2a: SELECT * FROM foo FOR SHARE NOWAIT;
id|data
--+----
 1|x   
(1 row)

step s2b: SELECT * FROM foo FOR UPDATE NOWAIT;
id|data
--+----
 1|x   
(1 row)

step s1a: SELECT * FROM foo FOR SHARE NOWAIT;
ERROR:  could not obtain lock on row in relation "foo"
step s1b: COMMIT;
step s2c: COMMIT;