Why back end testing is so important?

A back end is the engine of any client/server system. If the back end malfunctions, it may cause system deadlock, data corruption, data loss and bad performance. Many front ends log on to a single SQL server. A bug in a back end may put serious impact on the whole system. Too many bugs in a back end will cost tremendous resources to find and fix bugs and delay the system developments.

It is very likely that many tests in a front end only hit a small portion of a back end. Many bugs in a back end cannot be easily discovered without direct testing.

Back end testing has several advantages: The back end is no longer a "black box" to testers. Many bugs can be effectively found and fixed in the early development stage. Take Forecast LRS as an example; the number of bugs in a back end was more than 30% of total number of bugs in the project. When back end bugs are fixed, the system quality is dramatically increased.