How to: Create a Load Test Plug-In

Article
09/29/2016

You can create a load test plug-in to run code at different times while the load test is running. You create a plug-in to expand upon or modify the built in functionality of the load test. For example, you can code a load test plug-in to set or modify the load test pattern while the load test is running. To do this, you must create a class that inherits the ILoadTestPlugin interface. This class must implement the Initialize method of this interface. For more information, see ILoadTestPlugin.

Note

You can also create plug-ins for Web performance tests. For more information, see How to: Create a Web Performance Test Plug-In

Requirements

Visual Studio Enterprise

To create a Load Test Plug-in by using Visual C#

Open a Web performance and load test project that contains a Web performance test.

For more information, see How to: Create and Configure Test Projects for Automated Tests.
Add a load test to the test project and configure it to run a Web performance test.

For more information, see Creating load tests.
In Solution Explorer, right-click on the solution and 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.
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, and then select Microsoft.VisualStudio.QualityTools.LoadTestFramework.
Choose OK.

The reference to Microsoft.VisualStudio.QualityTools.LoadTestFramework 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 load test plug-in and select Add Reference.
The Add Reference dialog box is displayed.
Choose the Projects tab and select the Class Library Project.
Choose OK.
In the Code Editor, add a using statement for the Microsoft.VisualStudio.TestTools.LoadTesting namespace.
Implement the ILoadTestPlugin interface for the class that was created in the Class Library project. See the following Example section for a sample implementation.
After you have written the code, build the new project.
Right-click on the top node of the load test and then choose Add Load Test Plug-in.

The Add Load Test Plug-in dialog box is displayed.
Under Select a plug-in, select your load test plug-in class.
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 Load Test Plug-ins folder.
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

The following code shows a load test plug-in that runs custom code after a LoadTestFinished event occurs. If this code is run on a test agent on a remote machine and the test agent does not have a localhost SMTP service, the load test will remain in the "In progress" state because a message box will be open.

Note

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

using System;  
using Microsoft.VisualStudio.TestTools.LoadTesting;  
using System.Net.Mail;  
using System.Windows.Forms;  
  
namespace LoadTestPluginTest  
{  
    public class MyLoadTestPlugin : ILoadTestPlugin  
    {  
        LoadTest myLoadTest;  
  
        public void Initialize(LoadTest loadTest)  
        {  
            myLoadTest = loadTest;  
            myLoadTest.LoadTestFinished += new  
                EventHandler(myLoadTest_LoadTestFinished);  
        }  
  
        void myLoadTest_LoadTestFinished(object sender, EventArgs e)  
        {  
            try  
            {  
                // place custom code here  
                MailAddress MyAddress = new MailAddress("someone@example.com");  
                MailMessage MyMail = new MailMessage(MyAddress, MyAddress);  
                MyMail.Subject = "Load Test Finished -- Admin Email";  
                MyMail.Body = myLoadTest..Name + " has finished.";  
  
                SmtpClient MySmtpClient = new SmtpClient("localhost");  
                MySmtpClient.Send(MyMail);  
            }  
  
            catch (SmtpException ex)  
            {  
                MessageBox.Show(ex.InnerException.Message +  
                    ".\r\nMake sure you have a valid SMTP.", "LoadTestPlugin", MessageBoxButtons.OK, MessageBoxIcon.Warning, MessageBoxDefaultButton.Button1);  
            }  
        }  
    }  
}

Eight events are associated with a load test that can be handled in the load test plug-in to run custom code with the load test. The following is a list of the events that provide access to different periods of the load test run:

How to: Create a Load Test Plug-In

To create a Load Test Plug-in by using Visual C#

Example

See Also

Additional resources