What is performance,load and stress testing the web application?

Performance Tests

Performance Tests are tests that determine end to end timing (benchmarking) of various time critical business processes and transactions, while the system is under low load, but with a production sized database.  This sets ‘best possible’ performance expectation under a given configuration of infrastructure.  It also highlights very early in the testing process if changes need to be made before load testing should be undertaken.  For example, a customer search may take 15 seconds in a full sized database if indexes had not been applied correctly, or if an SQL 'hint' was incorporated in a statement that had been optimized with a much smaller database.  Such performance testing would highlight such a slow customer search transaction, which could be remediated prior to a full end to end load test.

 

 

 

Load Tests

Load Tests are end to end performance tests under anticipated production load.  The primary objective of this test is to determine the response times for various time critical transactions and business processes and that they are within documented expectations (or Service Level Agreements - SLAs).  The test also measures the capability of the application to function correctly under load, by measuring transaction pass/fail/error rates.  This test is one of the most fundamental load and performance tests and needs to be well understood.

 

This is a major test, requiring substantial input from the business, so that anticipated activity can be accurately simulated in a test situation.  If the project has a pilot in production then logs from the pilot can be used to generate ‘usage profiles’ that can be used as part of the testing process, and can even be used to ‘drive’ large portions of the Load Test. 

 

Load testing must be executed on “today’s” production size database, and optionally with a “projected” database.  If some database tables will be much larger in some months time, then Load testing should also be conducted against a projected database.  It is important that such tests are repeatable as they may need to be executed several times in the first year of wide scale deployment, to ensure that new releases and changes in database size do not push response times beyond prescribed SLAs.

 

 

Stress Tests

Stress Tests determine the load under which a system fails, and how it fails.  This is in contrast to Load Testing, which attempts to simulate anticipated load.  It is important to know in advance if a ‘stress’ situation will result in a catastrophic system failure, or if everything just “goes really slow”.  There are various varieties of Stress Tests, including spike, stepped and gradual ramp-up tests.  Catastrophic failures require restarting various infrastructure and contribute to downtime, a stress-full environment for support staff and managers, as well as possible financial losses.  This test is one of the most fundamental load and performance tests and needs to be well understood.