Attached is a rebase after TestLib.pm got a documentation in 6fcc40b1.
> The attached patch improves psql code coverage by adding a specific TAP test. > The 1709 tests take 4 seconds CPU (6.3 elapsed time) on my laptop. > > The infrastructure is updated to require perl module "Expect", allowing to > test interactive features such as tab completion and prompt changes. > > Coverage in "src/bin/psql" jumps from 40.0% of lines and 41.9% of functions > to 78.4% of lines and 98.1% of functions with "check-world".