What is Performance Testing and Why we need it?

3 Main types of Performance Testing:

1. Load Testing - testing system under load pressure during long time (usually from 1 hour till couple weeks).
2. Stress Testing - testing system under heavy load pressure during very short time (usually from couple seconds till 10-15 mins)
3. Benchmark Testing - testing limits of system. It should be added as additional verification for both Load and Stress Testing.

Examples and when we have to test it.

Load Testing has to be done for systems that run BAU and have support high volume for weekend, holidays and during high season. Rio 2016 broadcasting has to be tested for Load because it will be transmitted on all world during the long time (weeks). In addition we have to know limits (Benchmark Testing) when increasing volume of broadcasting has to be stopped or additional resources have to be added. 

Stress Testing is designed for verify capability of system to handle short but very high jumps in load of system. For example Power outage in City will be trigger for huge number phone calls that has to be tested by Stress Test and also we have to know limits of mobile provider that can be found by Benchmark Testing.

Now, when we know a base of performance testing, so we can make small calculation, if system is design and tested to manage 1M calls per hour, it means 217 users per sec can be connected to system or 16666 every min. If an analyse of traffic estimate 1000 users per min as maximum, then a system is ready to use, otherwise it can be reviewed and performance tuning has to be done.