Add behavioural tests for database functions

[rod-glover]

So far all we have is tests that the functions can be invoked without throwing an error. This doesn't give much assurance that they are actually working properly.

These functions were manually entered in pre-PyCDS times. More recently, they were brought under PyCDS management, but only minimal testing for them added at that time. History and usage suggests they work as intended, but we are updating some of them and with that it would be valuable to have tests.