How to distinguish stress testing from load testing, and what is their main difference?

The main difference between stress testing and load testing lies in their goals and conditions:

• Load Testing checks how the system performs under expected or slightly increased load. The goal is to ensure the system operates stably under normal conditions and can handle the planned number of users or operations.

• Stress Testing aims to evaluate the system under extremely high load, exceeding normal operational parameters, to identify its limits and behavior during failures.

Example:

• In load testing, you might simulate 1000 users to check response times.
• In stress testing, you increase the number of users to 2000 or more to see when the system begins to fail or degrade.

Thus, load testing verifies functionality within normal limits, while stress testing assesses resilience and behavior under overloads.