How to distinguish load testing from stress testing and performance testing, and how do they differ in goals and methodology?

Load Testing checks how the system operates under expected or slightly increased load to ensure it can handle the usual number of users or transactions without degradation.

Stress Testing aims to identify the system's limits by testing its behavior under extremely high load or resource shortages to understand how it behaves in critical conditions and how it recovers after failures.

Performance Testing is a broader concept that includes measuring various system characteristics (response speed, throughput, resource usage) under different load conditions.

Differences in purpose and methodology:

• Load Testing: goal — to verify stability and correctness under normal load.
• Stress Testing: goal — to determine the limits and resilience of the system under extreme conditions.
• Performance Testing: goal — to measure and optimize key performance indicators.

Example: during load testing, 1000 concurrent users are simulated; during stress testing, the load is increased to 5000 users to see when the system begins to fail.