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 step s2a: SELECT * FROM foo FOR SHARE NOWAIT; id data 1 x 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 step s1a: SELECT * FROM foo FOR SHARE NOWAIT; id data 1 x 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 step s2b: SELECT * FROM foo FOR UPDATE NOWAIT; id data 1 x step s1a: SELECT * FROM foo FOR SHARE NOWAIT; ERROR: could not obtain lock on row in relation "foo" step s1b: COMMIT; step s2c: COMMIT;