Parsed test spec with 3 sessions starting permutation: s1a s2a s3a s1b s2b s3b step s1a: SELECT * FROM foo FOR UPDATE; id data 1 x step s2a: SELECT * FROM foo FOR UPDATE; <waiting ...> step s3a: SELECT * FROM foo FOR UPDATE NOWAIT; ERROR: could not obtain lock on row in relation "foo" step s1b: COMMIT; step s2a: <... completed> id data 1 x step s2b: COMMIT; step s3b: COMMIT;