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

In case you need multiple expects of a test for different versions you have
to add .pg$(VERSION) at the end of the file.

For example if you want an expect file for PG11 you need to have two expect files:

  - CDB_SomethingTest_expect
  - CDB_SomethingTest_expect.pg11

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