How to: Create a Web Performance Test Plug-In
Web performance tests plug-ins enable you to isolate and reuse code outside the main declarative statements in your Web performance test. A customized Web performance test plug-in offers you a way to call some code as the Web performance test is run. The Web performance test plug-in is run one time for every test iteration. In addition, if you override the PreRequest or PostRequest methods in the test plug-in, those request plug-ins will run before or after each request, respectively.
You can create a customized Web performance test plug-in by deriving your own class from the WebTestPlugin base class.
You can use customized Web performance test plug-ins with the Web performance tests you have recorded, which enables you to write a minimal amount of code to obtain 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.
Note
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You can also create load test plug-ins. For more information, see How to: Create a Load Test Plug-In. |
Requirements
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Visual Studio Ultimate
To create a custom Web performance test plug-in
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Open a Web performance and load test project that contains a Web performance test.
For more information about how to create a Web performance and load test project, see How to: Create and Configure Test Projects for Automated Tests.
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In Solution Explorer, right-click on the solution and select Add and then choose New Project.
The Add New Project dialog box is displayed.
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Under Installed Templates, select Visual C#.
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In the list of templates, select Class Library.
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In the Name text box, type a name for your class.
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Choose OK.
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The new class library project is added to Solution Explorer and the new class appears in the Code Editor.
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In Solution Explorer, right-click the References folder in the new class library and select Add Reference.
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The Add Reference dialog box is displayed.
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Choose the .NET tab, scroll down, and select Microsoft.VisualStudio.QualityTools.WebTestFramework
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Choose OK.
The reference to Microsoft.VisualStudio.QualityTools.WebTestFramework is added to the Reference folder in Solution Explorer.
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In Solution Explorer, right-click on 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 plug-in and select Add Reference.
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The Add Reference dialog box is displayed.
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Choose the Projects tab and select the Class Library Project.
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Choose OK.
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In the Code Editor, write the code of your plug-in. First, create a new public class that derives from WebTestPlugin.
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Implement code inside one or both of the PreWebTest and PostWebTest event handlers. See the following Example section for a sample implementation.
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After you have written the code, build the new project.
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Open a Web performance test.
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To add the Web performance test plug-in, choose Add Web Test Plug-in on the toolbar.
The Add Web Test Plug-in dialog box is displayed.
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Under Select a plug-in, select your Web performance test plug-in class.
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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.
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Choose OK.
The plug-in is added to the Web Test Plug-ins folder.
Caution
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:
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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.
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Remove the plug-in from your test or the appropriate location and then add it back.
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The following code creates a customized Web performance test plug-in that adds an item to the WebTestContext that represents the test iteration.
After running the Web performance test, by using this plug-in you can see the added item that is named TestIteratnionNumer in the Context tab in the Web Performance Results Viewer.
using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.VisualStudio.TestTools.WebTesting;
namespace SampleRules
{
public class SampleWebTestPlugin : WebTestPlugin
{
// start counting iterations at 1 not 0
// so that the iteration number we give matches the run number
static int testIterationNumber = 1;
public override void PostWebTest(object sender, PostWebTestEventArgs e)
{
}
public override void PreWebTest(object sender, PreWebTestEventArgs e)
{
e.WebTest.Context["TestIterationNumber"] = testIterationNumber;
testIterationNumber++;
}
}
}
