What is Stress Testing in Software Testing?

Stress Testing is a software testing technique that determines the robustness of software by testing beyond the limits of normal operation. Stress testing is particularly important for critical software but is used for all types of software. Stress testing emphasizes robustness, availability, and error handling under a heavy load rather than what is correct behavior under normal situations. Stress testing is defined as a type of software testing that verifies the stability and reliability of the system. This test particularly determines the system on its robustness and error handling under extremely heavy load conditions. It even tests beyond the normal operating point and analyses how the system works under extreme conditions. Stress testing is performed to ensure that the system would not crash under crunch situations. Stress testing is also known as Endurance Testing or Torture Testing. 

Prerequisite – Types of Software Testing 

Characteristics of Stress Testing

1. Stress testing analyzes the behavior of the system after a failure.
2. Stress testing makes sure that the system recovers after failure.
3. It checks whether the system works under abnormal conditions.
4. It ensures the display of appropriate error messages when the system is under stress.
5. It verifies that unexpected failures do not cause security issues.
6. It verifies whether the system has saved the data before crashing or not.

Need For Stress Testing

• To accommodate the sudden surges in traffic: It is important to perform stress testing to accommodate abnormal traffic spikes. For example, when there is a sale announcement on the e-commerce website there is a sudden increase in traffic. Failure to accommodate such needs may lead to a loss of revenue and reputation.
• Display error messages in stress conditions: Stress testing is important to check whether the system is capable to display appropriate error messages when the system is under stress conditions.
• The system works under abnormal conditions: Stress testing checks whether the system can continue to function in abnormal conditions.
• Prepared for stress conditions: Stress testing helps to make sure there are sufficient contingency plans in case of sudden failure due to stress conditions. It is better to be prepared for extreme conditions by executing stress testing.

Purpose of Stress Testing

• Analyze the behavior of the application after failure: The purpose of stress testing is to analyze the behavior of the application after failure and the software should display the appropriate error messages while it is under extreme conditions.
• System recovers after failure: Stress testing aims to make sure that there are plans for recovering the system to the working state so that the system recovers after failure.
• Uncover Hardware issues: Stress testing helps to uncover hardware issues and data corruption issues.
• Uncover Security Weakness: Stress testing helps to uncover the security vulnerabilities that may enter into the system during the constant peak load and compromise the system.
• Ensures data integrity: Stress testing helps to determine the application’s data integrity throughout the extreme load, which means that the data should be in a dependable state even after a failure.

Stress Testing Process

The stress testing process is divided into 5 steps:

1. Planning the stress test: This step involves gathering the system data, analyzing the system, and defining the stress test goals.
2. Create Automation Scripts:  This step involves creating the stress testing automation scripts and generating the test data for the stress test scenarios.
3. Script Execution: This step involves running the stress test automation scripts and storing the stress test results.
4. Result Analysis: This phase involves analyzing stress test results and identifying the bottlenecks.
5. Tweaking and Optimization: This step involves fine-tuning the system and optimizing the code with the goal meet the desired benchmarks.

Types of Stress Testing

1. Server-client Stress Testing: Server-client stress testing also known as distributed stress testing is carried out across all clients from the server.
2. Product Stress Testing: Product stress testing concentrates on discovering defects related to data locking and blocking, network issues, and performance congestion in a software product.
3. Transactional Stress Testing: Transaction stress testing is performed on one or more transactions between two or more applications. It is carried out for fine-tuning and optimizing the system.
4. Systematic Stress Testing: Systematic stress testing is integrated testing that is used to perform tests across multiple systems running on the same server. It is used to discover defects where one application data blocks another application.
5. Analytical Stress Testing: Analytical or exploratory stress testing is performed to test the system with abnormal parameters or conditions that are unlikely to happen in a real scenario. It is carried out to find defects in unusual scenarios like a large number of users logged at the same time or a database going offline when it is accessed from a website.
6. Application Stress Testing: Application stress testing also known as product stress testing is focused on identifying the performance bottleneck, and network issues in a software product.

Stress Testing Tools

1. Jmeter: Apache JMeter is a stress testing tool is an open-source, pure Java-based software that is used to stress test websites. It is an Apache project and can be used for load testing for analyzing and measuring the performance of a variety of services. 
2. LoadNinja: LoadNinja is a stress testing tool developed by SmartBear that enables users to develop codeless load tests, substitutes load emulators with actual browsers, and helps to achieve high speed and efficiency with browser-based metrics.
3. WebLoad: WebLoad is a stress testing tool that combines performance, stability, and integrity as a single process for the verification of mobile and web applications.
4. Neoload: Neoload is a powerful performance testing tool that simulates large numbers of users and analyzes the server’s behavior. It is designed for both mobile and web applications. Neoload supports API testing and integrates with different CI/ CD applications.
5. SmartMeter: SmartMeter is a user-friendly tool that helps to create simple tests without coding. It has a graphical user interface and has no necessary plugins. This tool automatically generates advanced test reports with complete and detailed test results. 

Metrics of Stress Testing

Metrics are used to evaluate the performance of the stress and it is usually carried out at the end of the stress scripts or tests. Some of the metrics are given below.

1. Pages Per Second: Number of pages requested per second and number of pages loaded per second.
2. Pages Retrieved: Average time is taken to retrieve all information from a particular page.
3. Byte Retrieved: Average time is taken to retrieve the first byte of information from the page.
4. Transaction Response Time: Average time is taken to load or perform transactions between the applications.
5. Transactions per Second: It takes count of the number of transactions loaded per second successfully and it also counts the number of failures that occurred.
6. Failure of Connection: It takes count of the number of times that the client faced connection failure in their system.
7. Failure of System Attempts: It takes count of the number of failed attempts in the system.
8. Rounds: It takes count of the number of test or script conditions executed by the clients successfully and it keeps track of the number of rounds failed.

Benefits of Stress Testing

• Determines the behavior of the system: Stress testing determines the behavior of the system after failure and ensures that the system recovers quickly.
• Ensure failure does not cause security issues: Stress testing ensures that system failure doesn’t cause security issues. 
• Makes system function in every situation: Stress testing makes the system work in normal as well as abnormal conditions in an appropriate way.

Limitations of Stress Testing

1. Manual stress testing is complicated: The manual process of stress testing takes a longer time to complete and it is a complicated process.
2. Good scripting knowledge required: Good scripting knowledge for implementing the script test cases for the particular tool is required.
3. Need for external resources: There is a need for external resources to implement stress testing. It leads to an extra amount of resources and time.
4. Constantly licensed tool: In the case of a licensed stress testing tool, it charges more than the average amount of cost.
5. Additional tool required in case of open-source stress testing tool: In the case of some open-source tools, there is a need for a load testing tool additionally for setting up the stress testing environment.
6. Improper test script implementation results in wastage: If proper stress scripts or test cases are not implemented then there will be a chance of failure of some resources and wastage of time.