Gomez Web Load Testing Understanding Ramp Calculations

Gomez Web Load Testing – Ramp Calculation WLT supports Flat and Ramp-up scenarios No quick way to estimate usage without using Schedule Test UI A defect in UI estimator also affects calculation

Scenario = Ramp-up to 1000 Hours over 10 minutes then ramp-down to 500 users for 10 minutes We would think that the calculation is based on following theory but this is not the case… Flat Scenario = 1000 Virtual Users Flat for 20 Minutes VUH = 1000VU * (20min/60) = 334 – Simple calculation based on fraction of hour used (rounded-up) Ramp-up Differences Between Flat and Ramp Calculation

Calculate for 10 minutes =(1000* 10+ ( )*(1 + 10)/2) * (1/60) = 121 VUH Calculate for 10 minutes =(0* 10+ (1000-0)*(1 + 10)/2) * (1/60) = 92 VUH Understanding Ramp Calculation Ramp-up is not a straight-line calculation Formula to calculate is VUH = (fromVUs * duration + (toVUs - fromVUs)*(1 + duration )/2) * (1/60) VUs TIME (minutes)

Enter the target virtual users, duration and pick Flat/Ramp from drop-down Excel calculations determine ramp-up or down You can quickly enter multiple steps into the estimator Excel sheet is protected but no password required Download from FUSE or embedded Excel object Use the Excel Virtual User Estimator

FAQ Q: why is the estimator different from the WLT UI? A: the difference in calculations is a known defect that is being addressed in an upcoming maintenance release. Notification will be posted on FUSE as soon as this is available. Q: why is this still an estimate? A: during load tests there can be issues or errors that affect the total number of running virtual users (e.g. error rate) that the UI and Excel calculator cannot anticipate. You should always therefore claim that these are estimated usage rates that will be carefully monitoring and reported on during test execution.