Load testing involves verifying the program’s performance under normal or peak workload conditions. This analysis should not be confused with volume testing aimed at checking normal and extreme volumes of data: heavy load means the arrival of the maximum amount of data for a short time interval. Here you can draw an analogy to the typist’s work. When testing performed with extreme volumes of data, it should be determined whether the typist will be able to handle the draft of the large report, and when testing at extreme loads, the typist will be able to print at a rate of 50 words per minute.
Since load testing is affected by factor of time, it does not apply to many programs, for example, to the compiler or to payroll processing software. However, it can be used for programs that operate under variable loads, interactive or real-time programs, and process control programs. So, if it is assumed that the air traffic control system should track up to 200 air routes in its sector, then it should be tested at the maximum load by simulating the presence of 200 aircrafts. As far as there are no grounds for the appearance of the 201st aircraft in the sector, a further increase in the load will result in the system responding to an aircraft that will never appear. Additional testing at extreme loads can be a test simulating the simultaneous entry of a large number of aircrafts into the sector.
IT products are subjected to extreme workload that is beyond their operational capacity to check if these can handle high demand. Stress testing service is used to verify whether the software is durable and robust enough not to fail under unfavorable conditions.
Let us say the operating system supports execution of up to 15 tasks in multiprogram mode, then it is loaded by performing 15 tasks at the same time. If the time sharing system supports up to 65 terminals, subject it to the maximum load: connect 65 users to it that try to make simultaneous calls. (This is not a “situation that will never happen”, it really takes place when the system fails and the operator immediately restores its operability). To determine the response of the simulator system, use it to simulate the actions of the pilot undergoing training, such as moving the rudder to the left, turning on the brakes, lowering the flaps, lifting the front of the airplane, releasing the chassis, turning on the landing lights, turning to the left, and all these actions should be performed simultaneously.