Letra b
The regression tests can be run against an already installed and running server, or using a temporary installation within the build tree. Furthermore, there is a "parallel" and a "sequential" mode for running the tests. The sequential method runs each test script in turn, whereas the parallel method starts up multiple server processes to run groups of tests in parallel. Parallel testing gives confidence that interprocess communication and locking are working correctly. For historical reasons, the sequential test is usually run against an existing installation and the parallel method against a temporary installation, but there are no technical reasons for this.
To run the regression tests after building but before installation, type:
gmake check
To run the tests after installation (see Chapter 15), initialize a data area and start the server, as explained in Chapter 17, then type:
gmake installcheck
or for a parallel test:
gmake installcheck-parallel
https://www.postgresql.org/docs/8.4/regress-run.html