How to: Create a Request-Level Plug-In

Article
07/13/2012

Requests are the declarative statements that constitute Web performance tests. Web performance test plug-ins enable you to isolate and reuse code outside the main declarative statements in your Web performance test. You can create plug-ins and add them to an individual request as well as to the Web performance test that contains it. A customized request plug-in offers you a way to call code as a particular request is run in a Web performance test.

Every Web performance test request plug-in has a PreRequest method and a PostRequest method. After you attach a request plug-in to a particular http request, the PreRequest event will be fired before the request is issued and the PostRequest fired after the response is received.

You can create a customized Web performance test request plug-in by deriving your own class from the WebTestRequestPlugin base class.

You can use customized Web performance test request plug-ins with the Web performance tests you have recorded. Customized Web performance test request plug-ins enable you to write a minimal amount of code to attain a greater level of control over your Web performance tests. However, you can also use them with coded Web performance tests. For more information, see How to: Create a Coded Web Performance Test.

Requirements

Visual Studio Ultimate

To create a request-level plug-in

In Solution Explorer, right-click the solution, . select Add and then choose New Project.

The Add New Project dialog box is displayed.
Under Installed Templates, select Visual C#.
In the list of templates, select Class Library.
In the Name text box, type a name for your class and Choose OK.

The new class library project is added to Solution Explorer and the new class appears in the Code Editor.
In Solution Explorer, right-click the References folder in the new class library and select Add Reference.

The Add Reference dialog box is displayed.
Choose the .NET tab, scroll down, select Microsoft.VisualStudio.QualityTools.WebTestFramework and then choose OK

The reference to Microsoft.VisualStudio.QualityTools.WebTestFramework is added to the Reference folder in Solution Explorer.
In Solution Explorer, right-click the top node of the Web performance and load test project that contains the load test to which you want to add the Web performance test request test plug-in. Select Add Reference.

The Add Reference dialog box is displayed.
Choose the Projects tab, select the Class Library Project and then choose OK .
In the Code Editor, write the code of your plug-in. First, create a new public class that derives from WebTestRequestPlugin.
Implement code inside one or both of the PreRequest and PostRequest event handlers. See the following Example section for a sample implementation.
After you have written the code, build the new project.
Open the Web performance test to which you want to add the request plug-in.
Right-click the request to which you want to add the request plug-in, and select Add Request Plug-in.

The Add Web Test Request Plug-in dialog box is displayed.
Under Select a plug-in, select your new plug-in.
In the Properties for selected plug-in pane, set the initial values for the plug-in to use at run time.

Note

You can expose as many properties as you want from your plug-ins; just make them public, settable, and of a base type such as Integer, Boolean, or String. You can also change the Web performance test plug-in properties later by using the Properties window.
Choose OK.

The plug-in is added to the Request Plug-ins folder, which is a child folder of the HTTP request.
Warning

You might get an error similar to the following when you run a Web performance test or load test that uses your plug-in:

Request failed: Exception in <plug-in> event: Could not load file or assembly '<"Plug-in name".dll file>, Version=<n.n.n.n>, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.

This is caused if you make code changes to any of your plug-ins and create a new DLL version (Version=0.0.0.0), but the plug-in is still referencing the original plug-in version. To correct this problem, follow these steps:
1. In your Web performance and load test project, you will see a warning in references. Remove and re-add the reference to your plug-in DLL.
2. Remove the plug-in from your test or the appropriate location and then add it back.

Example

You can use the following code to create a customized Web performance test plug-in that displays two dialog boxes. On dialog box displays the URL that is associated with the request to which you attach the request add-in. The second dialog box displays the computer name for the agent.

Note

The following code requires that you add a reference to System.Windows.Forms.

using System;
using System.Collections.Generic;
using System.Windows.Forms;
using Microsoft.VisualStudio.TestTools.WebTesting;

namespace RequestPluginNamespace
{
    public class MyWebRequestPlugin : WebTestRequestPlugin
    {
        public override void PostRequest(object sender, PostRequestEventArgs e)
        {
            MessageBox.Show(e.WebTest.Context.AgentName);
        }
        public override void PreRequest(object sender, PreRequestEventArgs e)
        {
            MessageBox.Show(e.Request.Url);
        }
    }
}

Share via

How to: Create a Request-Level Plug-In

To create a request-level plug-in

Example

See Also

Tasks

Reference

Other Resources

Additional resources