Overview on LoadRunner

LoadRunner is  performance testing and load testing tool by Hewlett-Packard (since it acquired Mercury Interactive in 2007) for examining system behavior and performance, while generating actual load. 

It is the industry standard for application performance testing. The load testing tool helps us to prevent issues by detecting bottlenecks and to obtain an accurate picture of end-to-end system performance before going live. While the application is under load, LoadRunner accurately measures, monitors, and analyzes a system’s performance and functionality. Extremely flexible for organizations and projects of all sizes, LoadRunner software testing tool enables us to test a range of applications including mobile, Ajax, Flex, HTML 5, .NET, Java, GWT, Silverlight, SOAP, Citrix, ERP and legacy. LoadRunner can emulate hundreds or thousands of concurrent users to put the application through the rigors of real-life user loads, while collecting information from key infrastructure components (Web servers, database servers etc). The results can then be analyzed in detail, to explore the reasons for particular behavior.

LoadRunner Advantages

•    LoadRunner reduces the personnel requirement by replacing the human users with the Vusers (virtual users).

•    LoadRunner automatically records the performance of the client/server during test.

•    The numerous Vusers run on a single computer LoadRunner reduces the hardware requirements.

•    LoadRunner checks where performance delays occurs network/client delays.

•    It allows us to effectively control all Vusers from single point of control.

•    LoadRunner monitors the application performance online, enabling us to fine-tune our system during test execution.

•    LoadRunner checks where performance delays occur: network or client delays, CPU performance, I/O delays, database locking, or other issues at the database server. LoadRunner monitors the network and server resources to help us to improve performance.

•    Because LoadRunner tests are fully automated, we can easily repeat them as often as we need.

LoadRunner Components

LoadRunner consists of three components:

1. Virtual User Generator called as VuGen.
2. Controller.
3. Analysis.

1. Virtual User Generator (VuGen): 

The VuGen is a place to record and write automated scripts where it allows us to determine what actions we would like our Vusers or virtual users to perform within the application. It allows a software test professional to record/modify/write scripts for the application under test (AUT). We create scripts that generate a series of actions such as logging on, navigating through the application, and exiting the program. A performance tester records the script and then plays back and make modifications to the script if required. A tester may need to do correlation or parameterization etc.

2. Controller: 

After creating the script in VuGen, controller is used to run the script where it controls load generators and scenarios associated with them. The Controller takes the scripts that we have made and runs them through a schedule that we set up. Usually, LoadRunner use various machines called as Load Generators to generate load. We tell the Controller how many Vusers to activate, when to activate them, and how to group the Vusers and keep track of them. Performance tester connects each script in the scenario to the name of machine that is going to act as a Load Generator. During a load test, monitors are used by LoadRunner to monitor the performance of components under load. Overall, we can say that controller drives, organizes, manages, and monitors the load test.

3. Analysis: 

After running is completed, the result of the scenario is viewed using Analysis tool. The Results and Analysis program gives us all the results of the load test in various forms where it allows us to see summaries of data as well as the details of the load test for pinpointing problems or bottlenecks. This component creates the graphs for the performance tester to view. Graphs can also be merged to get a good analysis of the performance. Reports including all the necessary graphs can be saved in various formats like HTML and Microsoft Word format etc.

The LoadRunner Testing Process

There are five steps in LoadRunner Testing Process:

1. Planning the Test.
2. Creating the Vuser scripts.
3. Creating the Scenario.
4. Running the Scenario.
5. Analyzing Test Results.

1. Planning the Test:

A clearly defined test plan will ensure that the LoadRunner scenarios that we develop will accomplish our load testing objectives.

2. Creating the Vuser scripts:
Vusers emulate human users interacting with our client/server system. A Vuser script contains the actions that each virtual user performs during scenario execution.
In each Vuser script we determine the tasks that will be performed by each Vuser, performed simultaneously by multiple Vusers, and measured as transactions.

3. Creating the Scenario:
A scenario describes the events that occur during a client/server testing session. A scenario includes a list of machines that "host" Vusers; a list of Vuser scripts that the Vusers run; and a list of Vusers that run during the scenario. We create scenarios using the LoadRunner Controller.

4. Running the Scenario:
We emulate user load on the server by instructing multiple Vusers to perform tasks simultaneously. We can set the level of load by increasing and decreasing the number of Vusers that perform tasks at the same time.
Before we run a scenario, we have to set the scenario configuration. This determines how all the hosts and Vusers behave when we run the scenario. For each scenario, we create a list of scripts that Vusers run during scenario execution. We can run the entire scenario, individual Vusers, or groups of Vusers (Vuser Groups). While a scenario runs, LoadRunner measures and records the transactions that we defined in each Vuser script.

5. Analyzing Test Results:

We use LoadRunner's graphs and reports to analyze the server's performance after LoadRunner records the performance of the client/server system under different loads during scenario execution.


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