It is nothing but,it is a unit testing..................

Database testing is to check the "Data Integrity" and "Data 
Persistency".
Data Integrity means to measure the accuracy based on error 
detection (or) the reliability and correctness of data. 
Data Persistency means to check whether the data persist or 
not in the database.

Hope this helps.

While creating tests for your software you may come across 
database code that needs to be unit tested. The database 
extension has been created to provide an easy way to place 
your database in a known state, execute your database-
effecting code, and ensure that the expected data is found 
in the database.
For data base testing one must know about the structur of 
the database for ex.-- what is the query, how to handle & 
exicution of the query