Disadvantages of Big Bang Testing
Disadvantages of Big-Bang testing in a nutshell are - First it requires both stubs and drivers to test the independent components. Second because all components are merged once, it is difficult to find the cause of any failure. Finally, interface faults cannot be distinguished easily from other types of faults. [Source]
1. If there is a bug, you have to do extensive debugging to find it.
2. It only seems to be quick in theory but practically it may take long time to get an installable, runnable, testable build of all the units together and deployed in the test environment that it would have taken to test pieces of the overall system over time.
3. You must wait until all the units are ready for integration to start integration testing; you have delayed the finding of any integration bugs until that time. Why wait until all code is written to start integration? After all, the later you find the bug, the longer it will take to fix and the more it will cost.
Also see:
Big-Bang Testing
Integration Testing
Example of Integration & System Testing
Difference between Integration & System Testing
Integration Test Plan Templates
Integration & System Testing Checklist