LoadRunner

Introduction

LoadRunner is a performance testing tool originally developed by Mercury Interactive, which was acquired by Hewlett-Packard (HP) in 2006. It is now part of the Micro Focus suite of software testing tools. LoadRunner is designed to test the behavior and performance of applications under load, simulating multiple users concurrently accessing the application to identify and diagnose performance issues. This article delves into the technical aspects, architecture, and usage of LoadRunner, providing a comprehensive understanding for advanced users and professionals in the field of software testing.

Architecture

LoadRunner's architecture is composed of several key components:

Virtual User Generator (VuGen)

The Virtual User Generator (VuGen) is used to create scripts that emulate the actions of real users interacting with the application. These scripts are known as Vuser scripts. VuGen supports a wide range of protocols, including HTTP/HTTPS, FTP, and database protocols, among others. The scripting language used is typically C, although other languages like JavaScript and VBScript can also be used.

Controller

The Controller is the central component that manages and orchestrates the execution of Vuser scripts. It allows testers to define scenarios, which are sets of Vuser scripts and their execution schedules. The Controller also provides real-time monitoring and analysis of the test execution, enabling testers to observe the performance metrics and system behavior as the test progresses.

Load Generators

Load Generators are machines that execute the Vuser scripts during a test. They simulate the load by generating virtual users that interact with the application. Load Generators can be distributed across multiple machines to simulate a large number of concurrent users and to distribute the load more effectively.

Analysis

The Analysis component is used to process and interpret the data collected during the test execution. It provides detailed reports and graphs that help testers identify performance bottlenecks, analyze system behavior under load, and make informed decisions about performance improvements. The Analysis tool supports various metrics, including response times, throughput, and resource utilization.

LoadRunner software interface showing performance test results.

Protocols Supported

LoadRunner supports a wide range of protocols, making it a versatile tool for performance testing different types of applications. Some of the key protocols supported by LoadRunner include:

• **HTTP/HTTPS**: For testing web applications.
• **FTP**: For testing file transfer applications.
• **ODBC**: For testing database applications.
• **Oracle NCA**: For testing Oracle applications.
• **SAP GUI**: For testing SAP applications.
• **Citrix ICA**: For testing Citrix-based applications.
• **RDP**: For testing remote desktop applications.
• **Web Services**: For testing SOAP and RESTful web services.

Scripting and Correlation

Scripting

Creating effective Vuser scripts is crucial for accurate performance testing. VuGen provides a scripting environment that supports recording and editing of user actions. The recorded scripts can be enhanced with custom code to handle dynamic data, parameterization, and error handling. VuGen also supports correlation, which is the process of handling dynamic values that are generated by the server and need to be captured and reused in the script.

Correlation

Correlation is essential for ensuring that the Vuser scripts can handle dynamic data, such as session IDs and tokens, which change with each user session. VuGen provides automatic and manual correlation methods. Automatic correlation uses predefined rules to identify and handle dynamic values, while manual correlation allows testers to define custom rules and extract dynamic values using regular expressions or other methods.

Performance Testing Process

The performance testing process using LoadRunner typically involves the following steps:

Planning

Planning involves defining the objectives of the performance test, identifying the key performance indicators (KPIs), and determining the test environment and resources required. It also includes selecting the appropriate protocols and creating a test plan that outlines the scenarios to be tested.

Scripting

In this phase, Vuser scripts are created using VuGen. The scripts are recorded, enhanced, and correlated to accurately simulate user interactions with the application. Parameterization is also performed to ensure that the scripts use realistic data during execution.

Scenario Design

The Controller is used to design test scenarios, which involve defining the number of virtual users, their distribution across Load Generators, and the execution schedule. Scenarios can be designed to simulate different types of load, such as steady-state, ramp-up, and peak load.

Execution

The test scenarios are executed using the Controller, which manages the distribution of Vuser scripts across Load Generators and monitors the test execution in real-time. During execution, performance metrics are collected and monitored to observe the system's behavior under load.

Analysis

After the test execution, the collected data is analyzed using the Analysis component. Detailed reports and graphs are generated to identify performance bottlenecks, analyze system behavior, and make recommendations for performance improvements. The analysis phase is critical for understanding the impact of load on the application and identifying areas for optimization.

Advanced Features

LoadRunner offers several advanced features that enhance its capabilities for performance testing:

Service Virtualization

Service Virtualization allows testers to simulate the behavior of dependent systems that are not available or are difficult to access during testing. This enables end-to-end performance testing without the need for all components to be available.

Network Virtualization

Network Virtualization simulates different network conditions, such as latency, bandwidth, and packet loss, to test the application's performance under various network scenarios. This helps in understanding how network conditions impact the application's performance.

Continuous Integration

LoadRunner integrates with continuous integration (CI) tools like Jenkins, enabling automated performance testing as part of the CI pipeline. This ensures that performance issues are identified early in the development cycle and addressed promptly.

Cloud Testing

LoadRunner supports cloud-based performance testing, allowing testers to leverage cloud resources to generate load and execute tests. This provides scalability and flexibility in testing large-scale applications.

Best Practices

To achieve accurate and reliable performance testing results with LoadRunner, it is essential to follow best practices:

• **Define Clear Objectives**: Clearly define the objectives of the performance test, including the KPIs and the expected outcomes.
• **Use Realistic Data**: Use realistic data for parameterization to ensure that the Vuser scripts simulate real-world scenarios.
• **Monitor System Resources**: Monitor the system resources, such as CPU, memory, and disk usage, during test execution to identify resource bottlenecks.
• **Validate Scripts**: Validate the Vuser scripts to ensure that they accurately simulate user interactions and handle dynamic data correctly.
• **Conduct Baseline Tests**: Conduct baseline tests to establish a performance benchmark and compare subsequent test results against the baseline.
• **Analyze Results Thoroughly**: Analyze the test results thoroughly to identify performance bottlenecks and make informed recommendations for improvements.

Conclusion

LoadRunner is a powerful and versatile performance testing tool that enables testers to simulate real-world user interactions and identify performance issues in applications. Its comprehensive set of features, support for a wide range of protocols, and advanced capabilities make it an essential tool for performance testing professionals. By following best practices and leveraging LoadRunner's advanced features, testers can ensure that their applications perform optimally under load and provide a seamless user experience.

See Also

• Performance Testing
• Software Testing
• Continuous Integration
• Service Virtualization
• Network Virtualization