Performance testing is testing that is performed, from one perspective, to determine how fast some aspect of a system performs under a particular workload. It can also serve to validate and verify other quality attributes of the system, such as scalability, reliability and resource usage.
A load test is the simplest form of performance testing which is usually conducted to understand the behavior of the application under a specific expected load. This load can be the expected concurrent number of users on the application performing a specific number of transaction within the set duration. This test will give out the response times of all the important business critical transactions.
Stress testing is normally used to break the application. Double the number of users are added to the application and the test is run again until the application breaks down. This kind of test is done to determine the application's robustness in times of extreme load and helps application administrators to determine if the application will perform sufficiently if the current load goes well above the expected load.
Outcome of peformance testing can be:
1. hit per second
2. throughput
3. Response time etc