Code a custom validation rule for a web performance test
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
You can create your own validation rules. To do this, you derive your own rule class from a validation rule class. Validation rules derive from the ValidationRule base class.
Note
You can also create custom extraction rules. For more information, see Create custom code and plug-ins for load tests.
Note
Web performance and load test functionality is deprecated. Visual Studio 2019 is the last version where web performance and load testing will be fully available. For more information, see the Cloud-based load testing service end of life blog post. To reduce the impact on users some minimum support is still available in Visual Studio 2022 Preview 3 or later. Users should also note web performance and load test functionality only supports Internet Explorer which is not available on Windows 11 and some versions of Windows 10. Read more on Internet Explorer Lifecycle policy.
To create custom validation rules
Open a Test Project that contains a web performance test.
(Optional) Create a separate Class library project in which to store your validation rule.
Important
You can create the class in the same project that your tests are in. However, if you want to reuse the rule, it is better to create a separate Class library project in which to store your rule. If you create a separate project, you must complete the optional steps in this procedure.
(Optional) In the Class library project, add a reference to the Microsoft.VisualStudio.QualityTools.WebTestFramework DLL.
Create a class that derives from the ValidationRule class. Implement the Validate and RuleName members.
(Optional) Build the new Class library project.
(Optional) In the Test Project, add a reference to the Class library project that contains the custom validation rule.
In the Test Project, open a web performance test in the Web Performance Test Editor.
To add the custom validation rule to a web performance test request, right-click a request and select Add Validation Rule.
The Add Validation Rule dialog box appears. You will see your custom validation rule in the Select a rule list, together with the predefined validation rules. Select your custom validation rule and then choose OK.
Run your web performance test.
Example
The following code shows an implementation of a custom validation rule. This validation rule mimics the behavior of the predefined Required Tag validation rule. Use this example as a starting point for your own custom validation rules.
Warning
Public properties in the code for a custom validator cannot have null values.
using System;
using System.Diagnostics;
using System.Globalization;
using Microsoft.VisualStudio.TestTools.WebTesting;
namespace SampleWebTestRules
{
//-------------------------------------------------------------------------
// This class creates a custom validation rule named "Custom Validate Tag"
// The custom validation rule is used to check that an HTML tag with a
// particular name is found one or more times in the HTML response.
// The user of the rule can specify the HTML tag to look for, and the
// number of times that it must appear in the response.
//-------------------------------------------------------------------------
public class CustomValidateTag : ValidationRule
{
/// Specify a name for use in the user interface.
/// The user sees this name in the Add Validation dialog box.
//---------------------------------------------------------------------
public override string RuleName
{
get { return "Custom Validate Tag"; }
}
/// Specify a description for use in the user interface.
/// The user sees this description in the Add Validation dialog box.
//---------------------------------------------------------------------
public override string RuleDescription
{
get { return "Validates that the specified tag exists on the page."; }
}
// The name of the required tag
private string RequiredTagNameValue;
public string RequiredTagName
{
get { return RequiredTagNameValue; }
set { RequiredTagNameValue = value; }
}
// The minimum number of times the tag must appear in the response
private int MinOccurrencesValue;
public int MinOccurrences
{
get { return MinOccurrencesValue; }
set { MinOccurrencesValue = value; }
}
// Validate is called with the test case Context and the request context.
// These allow the rule to examine both the request and the response.
//---------------------------------------------------------------------
public override void Validate(object sender, ValidationEventArgs e)
{
bool validated = false;
int numTagsFound = 0;
foreach (HtmlTag tag in e.Response.HtmlDocument.GetFilteredHtmlTags(RequiredTagName))
{
Debug.Assert(string.Equals(tag.Name, RequiredTagName, StringComparison.InvariantCultureIgnoreCase));
if (++numTagsFound >= MinOccurrences)
{
validated = true;
break;
}
}
e.IsValid = validated;
// If the validation fails, set the error text that the user sees
if (!validated)
{
if (numTagsFound > 0)
{
e.Message = String.Format("Only found {0} occurrences of the tag", numTagsFound);
}
else
{
e.Message = String.Format("Did not find any occurrences of tag '{0}'", RequiredTagName);
}
}
}
}
}
Imports System
Imports System.Diagnostics
Imports System.Globalization
Imports Microsoft.VisualStudio.TestTools.WebTesting
Namespace SampleWebTestRules
'-------------------------------------------------------------------------
' This class creates a custom validation rule named "Custom Validate Tag"
' The custom validation rule is used to check that an HTML tag with a
' particular name is found one or more times in the HTML response.
' The user of the rule can specify the HTML tag to look for, and the
' number of times that it must appear in the response.
'-------------------------------------------------------------------------
Public Class CustomValidateTag
Inherits Microsoft.VisualStudio.TestTools.WebTesting.ValidationRule
' Specify a name for use in the user interface.
' The user sees this name in the Add Validation dialog box.
'---------------------------------------------------------------------
Public Overrides ReadOnly Property RuleName() As String
Get
Return "Custom Validate Tag"
End Get
End Property
' Specify a description for use in the user interface.
' The user sees this description in the Add Validation dialog box.
'---------------------------------------------------------------------
Public Overrides ReadOnly Property RuleDescription() As String
Get
Return "Validates that the specified tag exists on the page."
End Get
End Property
' The name of the required tag
Private RequiredTagNameValue As String
Public Property RequiredTagName() As String
Get
Return RequiredTagNameValue
End Get
Set(ByVal value As String)
RequiredTagNameValue = value
End Set
End Property
' The minimum number of times the tag must appear in the response
Private MinOccurrencesValue As Integer
Public Property MinOccurrences() As Integer
Get
Return MinOccurrencesValue
End Get
Set(ByVal value As Integer)
MinOccurrencesValue = value
End Set
End Property
' Validate is called with the test case Context and the request context.
' These allow the rule to examine both the request and the response.
'---------------------------------------------------------------------
Public Overrides Sub Validate(ByVal sender As Object, ByVal e As ValidationEventArgs)
Dim validated As Boolean = False
Dim numTagsFound As Integer = 0
For Each tag As HtmlTag In e.Response.HtmlDocument.GetFilteredHtmlTags(RequiredTagName)
Debug.Assert(String.Equals(tag.Name, RequiredTagName, StringComparison.InvariantCultureIgnoreCase))
numTagsFound += 1
If numTagsFound >= MinOccurrences Then
validated = True
Exit For
End If
Next
e.IsValid = validated
' If the validation fails, set the error text that the user sees
If Not (validated) Then
If numTagsFound > 0 Then
e.Message = String.Format("Only found {0} occurrences of the tag", numTagsFound)
Else
e.Message = String.Format("Did not find any occurrences of tag '{0}'", RequiredTagName)
End If
End If
End Sub
End Class
End Namespace