Thursday 26 April 2012

STRESS TESTING

STRESS TESTING: 
It is done to evaluate the application's behaviour beyond normal or peak load conditions. It is basically testing the functionality of the application under high loads. Normally these are related to synchronization issues, memory leaks or race conditions etc. Some testing experts also call it as fatigue testing. Sometimes, it becomes difficult to set up a controlled environment before running the test. Example of Stress testing is:

A banking application can take a maximum user load of 20000 concurrent users. Increase the load to 21000 and do some transaction like deposit or withdraw. As soon as you did the transaction, banking application server database will sync with ATM database server. Now check with the user load of 21000 does this sync happened successfully. Now repeat the same test with 22000 thousand concurrent users and so on.
Spike test is also a part of stress testing which is performed when application is loaded with heavy loads repeatedly and increase beyond production operations for short duration.
Stress Testing helps to determine:
  • Errors in slowness & at peak user loads
  • Any security loop holes with over loads
  • How the hardware reacts with over loads
  • Data corruption issues at over loads

Testing with the intent of determining how well a product performs when a load is placed on the system resources that nears and then exceeds capacity.

Under stress testing, various activities to overload the existing resources with excess jobs are carried out in an attempt to break the system down. Negative testing, which includes removal of the components from the system is also done as a part of stress testing. Also known as fatigue testing, this testing should capture the stability of the application by testing it beyond its bandwidth capacity.
The purpose behind stress testing is to ascertain the failure of system and to monitor how the system recovers back gracefully. The challenge here is to set up a controlled environment before launching the test so that you could precisely capture the behaviour of system repeatedly, under the most unpredictable scenarios.
Stress Testing Goal:
The goal of the stress testing is to analyse post-crash reports to define the behaviour of application after failure. The biggest issue is to ensure that the system does not compromise with the security of sensitive data after the failure. In a successful stress testing, the system will come back to normality along with all its components, after even the most terrible break down.
Example:
As an example, a word processor like Writer1.1.0 by OpenOffice.org is utilized in development of letters, presentations, spread sheets etc… Purpose of our stress testing is to load it with the excess of characters.
To do this, we will repeatedly paste a line of data, till it reaches its threshold limit of handling large volume of text. As soon as the character size reaches 65,535 characters, it would simply refuse to accept more data. The result of stress testing on Writer 1.1.0 produces the result that, it does not crash under the stress and that it handle the situation gracefully, which make sure that application is working correctly even under rigorous stress conditions.

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