Stress Testing of Web Applications

Stress Testing is performed to identify the issues of the application that can arise only in cases of extreme software and hardware conditions. These conditions may be heavy loads, extreme concurrency or limited resources. Stress Testing identifies the breaking point of the application and related system discrepancies that may occur just before that. Such inconsistencies may be:

- Loss or corruption of data.

- Unnecessary high resource utilization

.- Failure of application components to respond.

- Surfacing of new and un-handled exceptions.

Stress on an application can be due to one or more of the following reasons:

- Excessive user or data

- Denial of service

- Sudden spike in user transactions

- Unexpected outages

Steps for Stress Testing -

Step 1: Identify the test objectives

- The different ways that the system can possibly fail.

- Parameters to consider for building defenses against possible failures.

- Identify the behavior of the system under challenging situations.

- Ensure the stability of the system under stressful conditions.     

   

Step 2: Identify the main scenarios

-  Select scenarios critical to the overall application performance.

- Try operations that affect performance.

- Define scenarios based on potential bottlenecks through load testing and stress test in these areas.

Step 3: Identify the workload

- Incrementally increase the load and record the application performance under such conditions. Here, the key is to test the system with various workloads until a significant failure can be created.

The following activities help to identify the correct workload for stress testing:

- Observe the distribution of work

- Estimate the peak user load

- Simulate the anti-profile workload

Step 4: Identify the metrics

Metrics help to identify the potential problem areas in a system or application.The different types of metric categories are:

- Processor Utilization

- Memory Consumption

- Process recycles

- Available memory

- Utilized memory

- Disk utilization

- Network utilization

- Transaction Rate

- Successful transactions

- Failed transactions

- Successful orders

- Failed orders

- Rate of contention

- Deadlocks

- Thread allocation

- Transaction time

Step 5: Creation of Test Cases

In addition to workload profiles and key scenarios, additional parameters such as performance objectives, workload characteristics, test environment, test data and identified metrics are required to design a test case. The expected results should be mentioned for each test in such a way that the test can be marked as a pass or fail after its execution.

Step 6: Load Simulation

- Validate the test environment as expected.

- Ensure the correct configuration of the test and the test environment for metrics collection.

- Quickly execute a smoke test to ensure that the test script and the performance counters are correctly working.

- Reset and start the system.

Step 7: Result Analysis

Analyze and compare the results as per the accepted level for each metric. In case of any issues:

- Review the design.

- Review the code.

- Run the stress tests in environments where debugging is possible.

Conclusion

In practice, stress testing in generally applied in application testing, transaction testing and system testing. Exploratory stress testing is applied by subjecting the system to conditions that are very unlikely to occur. A stress test is sometimes confused with loadtest, which is a milder form of testing. Stress testing very brutally emphasizes on the robustness, reliability, stability and scalability of a web application.