What is Load Testing and its Approach

Load testing is the simplest form of performance testing
Load testing is the simplest form of performance testing

Any product before its launch in the market is subjected to numerous tests. These tests aim to explore product behavior and performance level under different possible demand scenarios and provide feedback for development of a robust product. Likewise, the process of software development also involves use of different tests including regression testing, integration testing, load testing and so on.

Each of these tests involves a specific procedure to check specific parameters. While regression testing looks into the effect of modifications on software, integration testing looks into interaction of software and hardware components, and load testing checks the software’s capacity to handle the actual demand of an inflated number of end users.

In definitional terms, load testing is the process of subjecting a computer, peripheral, server, network or application to a work level approaching the limits of its specifications.  One of the primary tests, load testing is a part of a more general process known as performance testing, which assesses the speed and effectiveness of the application to generate results within a specified time.

Load testing is the simplest form of performance testing. During load testing, the software application or IT system is subjected to ordinary stress in order to confirm if it can perform as intended under normal conditions. It is different from stress testing, where the system is overloaded till it breaks by applying unrealistic or unlikely load scenarios, and soak testing which is used to determine if the system can sustain the continuous expected load. However, load test becomes stress test if the application fails to perform even on expected load. The Microsoft Performance Testing Guidance for Web Applications states in this regard: “A load test enables you to measure response times, throughput rates, and resource-utilization levels, and to identify your application’s breaking point, assuming that the breaking point occurs below the peak load condition.”

Importance of Load Testing

Primarily, load testing is conducted to understand the behavior of the application under a specific expected load. It provides the means to confirm whether the application or software would serve the end users satisfactorily, and if not then bottlenecks and elements causing degradation.

To cite an example, as per statista.com, global e-commerce is expected to generate a revenue of USD 2.3 trillion by 2018. All the transactions would be carried out through various applications where most of the time multiple users would be engaged in buying and selling from the same application. The success of such a model depends on reliable, stable and cost-effective web-based applications.  The only means to check whether the application is able to service such multiple users and is stable in behavior is through efficient load testing where each scenario is checked.

An Ideal Approach Towards Load Testing

As already discussed, the basic purpose of load testing is to determine the application’s behavior under both normal and anticipated load conditions. The following steps can be implemented to optimize the process of load testing:

  1. Before starting with any load test, it is important to make note of desired parameters, such as response time and memory utilization, and their acceptable performance criteria.
  2. The next step is to identify a key scenario and preparation of workload model. The model should start with a small number of virtual users and gradually increment the load to predefined target load levels. The model should allow for observation of the desired parameters at successive load levels.
  3. Using the data on parameters, key scenario and workload model with target load levels, a metric has to be created which helps to identify most relevant information related to performance objectives and potential bottlenecks.
  4. Next, based upon these metrics, the load test has to be scripted and executed. The load test should strictly follow workload model and metrics.
  5. Then, an analysis of the captured data and comparison of the results against the metric’s accepted level needs to be done to determine whether the application’s performance shows a trend toward or away from the performance objectives.

Input and Output

Input Parameters: Based on the above approach, a number of input parameters can be identified:

  • Number of concurrent users the application is intended to serve simultaneously (target load levels).
  • Performance parameters and their acceptance criteria.
  • Critical performance scenarios
  • Workload models
  • Feedback mechanism from user, tester and developer

Output Parameters:

  • Behavior of the application at various load levels and satisfactory performance load levels
  • Potential bottlenecks that need to be analyzed though white box testing
  • Performance parameters

The success of any application depends on its performance and response time when multiple users utilize the application at the same time. An application with high response time and poor performance deters users and consequently would be unsuccessful.

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