The best way to avoid problems on your system is to test prior to implementation. Most users only think of testing their application code. It is also necessary to test other aspects of the system including administration scripts and applications, such as backup software, hardware, middleware, and other infrastructure.
Testing is a long and meticulous process if done properly. There are three types of testing:
Limits testing — Exceeds hardware and software system limits and ensures system reliability
End-to-end testing — Examines an entire operation, checks the integrity of individual processes, and eliminates compatibility issues between processes, for example, looking at the order entry process from the customer's phone call to the delivery of goods
Unit testing — Examines a process in isolation; unit testing should be done during early development and again, prior to implementation, as the initial step in the user acceptance process
You can also run tests on the individual system hardware components in isolation to ensure there are no faults with any item. Once this testing is complete, you can run a stress test to test the items together. A well designed test includes your application components, making an end-to-end test possible. For a complete check of the system, execute the stress test while running at full capacity, and then simulate a crash of the system to check system resiliency.
Limits testing — Exceeds hardware and software system limits and ensures system reliability