Load Testing evaluates how a software application behaves when multiple users access it simultaneously. It is a non-functional software testing process in which the behaviour and performance of a software application are tested under a specific expected load. Load Testing aims to resolve performance bottlenecks and ensure stability and smooth functioning of a software application before deployment.
Since Load testing is the practice of modelling the expected usage of a software program by simulating many users accessing the program concurrently, it is most relevant for multi-user systems. Load testing more often than not simulates actual use instead of testing using analytical or theoretical modelling.
Load and performance testing analyses the software intended for a multi-user audience by subjecting it to a number of virtual and live users while monitoring performance measurements under these different loads. The test environment in which load testing is usually conducted matches with the production environment before the system is permitted to go live.
Some points that a test engineer should note while executing load testing:
- The application should undergo functional testing.
- Unique data should be available in a large number in the data pool
- The number of users should be finalised for each script or scenario
- The creation of detailed logs should be avoided to conserve the disk IO space
- Downloading of images on the site should be avoided
- The consistency of response time over the elapsed period should be logged and compared with various test runs.
Why do we need load testing?
- It guarantees the system’s consistency and performance.
- If there are code changes in the application that may affect the application’s performance, then load testing is necessary.
- It is essential as it reproduces real user scenarios.
- It helps identify the system’s bottlenecks.
Steps to perform load testing:
- Create a test environment that is close to the production environment in terms of hardware, software specifications, network, etc.
- Load test scenarios: A test scenario is a combination of scripts and virtual users executed during a testing session. The scenarios could either be manual or goal-oriented.
- Determine load testing transactions for an application
- Prepare the data for each transaction
- The number of users accessing the system needs to be predicted
- Determine connection speeds: some users could be using leased lines for connection while others may be using use dial-up
- Determine various browsers and operating systems used by the users
- A configuration of all the servers such as application, web and DB servers
- Execute test scenario and monitor, collecting various metrics
- Analyse the results: The results are analysed after executing the load test scenarios. The load test scenario can be inspected with the help of LoadRunner online monitors like:
- System resource
- Run-time transaction
- Network delay
- Web resource
Make recommendations post the analysis of the results.
- Fine-tune the system
- Re-test: The final step of the process depends on the test result: if the test fails, the same process must be repeated until the test result passes, and all the defects are fixed.
Methods of load testing:
- Manual Load Testing: Load testing can be done manually, but it is not advised where we need to test the application for higher loads. Also, this method does not produce repeatable results, nor can it provide measurable levels of stress on an application and is very tough to coordinate.
- In-house developed load testing tools: Realising the importance of load testing, an organization may build its own tools to execute load tests.
- Open source load testing tools: Several load testing tools are available as open-source and free of charge. They are the best bet if the company is on a tight budget.
- Enterprise-class load testing tools: These come with capture/playback facility. They are meant to support a large number of protocols and can simulate a huge number of users.
Some of the main objectives of using load testing are:
- It is used to determine the maximum quantity of software applications without important/significant performance breakdown.
- It helps identify the total count of users that can access the application simultaneously.
- It answers whether the latest infrastructure can run the software application or not and determines the sustainability of the application involving extreme user load.
Load testing is important if the application, system, or service is liable to a service level agreement or SLA. It determines a system’s behaviour under both normal and anticipated peak load conditions. It helps identify the maximum operating capacity as well as bottlenecks. Load testing helps determine which element is the root cause for degradation.
Here, it is helpful to understand the difference between Load testing and stress testing:
Load testing identifies the system’s bottlenecks under various workloads and checks how the system reacts when the load gradually increases.
Stress testing: When the load added on the system is raised beyond normal usage patterns to test its response at unusually high or peak loads, it is known as stress testing. It determines the breaking point of the system: it aims to reveal the maximum point after which it breaks.
Based on specific scenarios, the term “load testing” is often used synonymously with concurrency testing, software performance testing, reliability testing and volume testing. These are all types of non-functional testing.
Load testing tools:
There are various load testing tools available in the market, some of them are commercial, and some are open-source tools. Some of the most common tools are:
- Apache JMeter
- HP Performance Tester
Load testing helps:
- Identify performance bottlenecks before production
- Improve the scalability of the system
- Minimize the risk related to system downtime
- Bring down the costs of failure
- Enhance customer satisfaction
But there are a couple of disadvantages of load testing: firstly, one needs programming knowledge to be able to use the load testing tools; secondly, tools can be expensive as prices are based on the number of virtual users that it supports.
In all this, it is essential that performance engineers dedicate significant time and thought over each test run’s objectives and their expectations from the system under test. Before investing in building complex, time-consuming scenarios, it is vital to have clear goals for the tests.
To sum it up:
- Load testing is a kind of software testing that determines the performance of a system under real-life load conditions. It is a part of performance testing which helps learn about the software’s effectiveness and ability.
- Load testing expands the scalability and increases the stability/constancy of the application before it is available for production.
- It helps spot the maximum operating capacity of applications as well as system bottlenecks.
- Loading testing is essential: if ignored, it can cause financial losses.
- With the various load testing tools, one can deliver a quality product that will not crash when a maximum number of users use it simultaneously.
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