Adding tests consists in adding 2 files in this directory: one file
containing the sql code and another containing the expected output.

Example, to add a test for CDB_Something function, you'd add:

 - CDB_SomethingTest.sql
 - CDB_SomethingTest_expect

To easy the generation of the expected file you can initially omit it,
then run "make -C .. installcheck" from the top-level dir and copy
../results/test/CDB_SomethingTest.out to CDB_SomethingTest_expect chopping
off the first line:

 make -C .. installcheck
 tail -n +2 ../results/test/CDB_SomethingTest.out > CDB_SomethingTest_expect