Getting Started

Getting Started

Load simulation against a Web application is usually implemented through a combination of hardware- and software-based emulation of users executing real-world transaction scenarios against an application. The hardware method usually requires several dedicated test clients and represents one user per client. This method can be quite expensive and time consuming to maintain, given the required hardware resources for heavy stress testing. The hardware method is neither the most effective nor the most efficient method of stress testing, but due to the nature of a given application, hardware-based stress testing maybe the only choice. With the software method, user transaction scenarios are typically recorded or captured by a software tool and converted to test scripts during a walkthrough of the application. When playing back or executing a test script, one machine typically acts as a controller to distribute the test script across multiple client machines. As the test runs, the controller produces load in unison to simulate many virtual users, and when the test is complete, it summarizes the test data from all of the clients. These virtual users create load on the backend servers and help to determine the stability and responsiveness of the Web application.

There are many software-based stress testing tools. While the purpose of these tools is to produce load by simulating many users, the syntax used for creating stress scripts and the load engine varies per tool. The stress tool discussed throughout this book is Microsoft Application Center Test (ACT). The goal of this chapter is not necessarily to make you an expert at using ACT but to give you a brief overview of the product and discuss the core concepts and features we frequently use. We will also demonstrate and explain how to create and verify dynamic test scripts using ACT to accurately simulate load against a .NET Web application

What is ACT?

ACT is a software-based stress testing tool that applies load to Web servers, so that you can capture performance metrics, analyze and diagnose performance problems, and make capacity decisions about your Web applications. You apply load to a Web application using ACT by recording or manually creating a test script, which simulates many simultaneous browser connections requesting pages defined by a user scenario.

Installing Microsoft ACT

ACT is included with Visual Studio .NET Enterprise and Architect editions. Many different components comprise Visual Studio .NET, but for this book, we will only select the components necessary to run ACT as a stand-alone client.

The installation process is broken down into three major steps. Step 1 is shown in Figure 3-1.

Figure 3-1. The Install Windows Component Update dialog box

Select Step 1: The Install Windows Component Update dialog box to update the system components. This option is available in the Installation dialog box if the update is required for your system. If a component update is not required, this option is not available.

NOTE
If you are running an anti-virus program during setup, warnings may be displayed as setup runs scripts that access the file system object.

After updating the system components, the Installation dialog box enables Step 2: Install Visual Studio .NET. Select Step 2 to install Visual Studio .NET. Our installation will be very slim because we are only installing the components required to run ACT. If you require the flexibility of creating and running projects and test scripts directly from the integrated Visual Studio IDE, you must add additional components. Application Center Test is located under Enterprise Development Tools in the Select Items to Install list, as shown in Figure 3-2, and should be checked by default.

Figure 3-2. Selecting options for installation

Selecting Step 3: Service Releases Check is optional but highly recommended to ensure that you have all of the latest patches or fixes.