There are three basic suites of tests: - pg_regress, which is as you say a set of SQL scripts run on a running server with generated output compared to the exp

There are three basic suites of tests: - pg_regress, which is as you say a set of SQL scripts run on a running server with generated output compared to the expected output. There could be multiple expected outputs, see for example float tests. - pg_isolation_test, which is a part you are misunderstanding. This facility has been introduced with SSI (serializable transactions) to test concurrency. - TAP tests (author of the replication/backup/recovery part here), which has roughly three test suites: -- src/bin/ to test all the in-core binaries -- src/test/ssl to test SSL configurations. This has proved to be useful lately when moving all the SSL parameters to be reloadable. -- src/test/recovery to test all the kind of replication scenarios. There are as well modules in src/test/modules that use TAP tests to run regressions on pg_dump, commit timestamps and extension interactions.