The regression tests are a comprehensive set of tests for the SQL
   implementation in PostgreSQL.  They test
   standard SQL operations as well as the extended capabilities of
   PostgreSQL.  The test suite was
   originally developed by Jolly Chen and Andrew Yu, and was
   extensively revised and repackaged by Marc Fournier and Thomas
   Lockhart.  From PostgreSQL 6.1 onward
   the regression tests are current for every official release.