Software Testing - Performance Testing

Performance testing is about checking how a system behaves under certain workloads — focusing on speed, stability, and scalability rather than correctness of functionality.

Here are the basics:

1. Purpose of Performance Testing

  • Validate speed — Does the application respond quickly enough?

  • Check scalability — Can it handle more users or bigger data loads without breaking?

  • Ensure stability — Does it stay reliable under continuous or high load?

2. Key Performance Testing Types

Type Goal
Load Testing Measures system behavior under expected workload.
Stress Testing Pushes the system beyond normal limits to find breaking points.
Soak/Endurance Testing Checks for issues over long durations (e.g., memory leaks).
Spike Testing Tests reaction to sudden increases in load.
Scalability Testing Examines how well the system scales with more users/resources.
Volume Testing Focuses on large data processing rather than user load.

3. Key Metrics to Measure

  • Response Time — How long it takes to get a result.

  • Throughput — Requests or transactions per second.

  • Concurrency — Number of simultaneous active users.

  • Resource Usage — CPU, memory, disk, network utilization.

  • Error Rate — Percentage of failed or incorrect requests.

4. Basic Process

  1. Define objectives — What performance goals do you have? (e.g., "support 5,000 concurrent users with < 2s response time")

  2. Plan the test — Select scenarios, workloads, and metrics.

  3. Prepare environment — Use production-like hardware, network, and software.

  4. Create test scripts — Simulate realistic user interactions.

  5. Run the tests — Start with baseline loads, then scale up.

  6. Analyze results — Identify bottlenecks and trends.

  7. Optimize and retest — Tune system and repeat testing until goals are met.

5. Common Tools

  • JMeter (open source)

  • LoadRunner / Performance Center

  • Gatling

  • k6

  • Locust

  • Apache Bench (ab)