What to check during load testing

You should watch for monitoring alarms during all your tests, but especially with load testing, which is designed to exercise uncovering system issues. If there are memory leaks or leaks of other resources, this is the test to find them. Load testing has to be performed by automated scripts, but writing the checks is at least as much work as generating the load. A single command to change the system’s state may need many tests to verify it. Write a generic check function that you can expand for whatever tests you are performing, and use your system monitoring; see Chapter 10, Maintainability.

At the most basic level, you can run load testing and check for any catastrophic events – the application crashing or unhandled exceptions. The next level of checking is verifying that each operation is successful. For every user creation command, for instance, check that a user exists. You should also routinely check the logs for error messages...