Dynamic Targets

A Dynamic Target is a unique parameter or variable used by the application to generate information like a unique user ID or session ID. These values are generated by the web server and sent to the browser, which then later returns that value back to the server, so that the application can match the new request to a previous HTTP transaction. To accurately simulate users via virtual users, it is important to correctly return these Dynamic Targets during the load test execution.

Note! Dynamic targets are also used to data drive the load test profile.

Auto-detected Dynamic Targets

If Test Studio detected any possible Dynamic Targets in the HTTP traffic, a list of those targets will appear after you capture a user profile. In this screen, you can select which Dynamic Targets the load test should use while running the test by checking the box next to the name of the Dynamic Target.

In most situations, you should select all dynamic targets, unless you have a specific reason to deselect a particular dynamic target.

Properties

Each dynamic target lists four properties:

• Target: The name of the parameter or variable from the original URL.
• From: The step number of the response in which the target was detected.
• To: The step number of the request in which the target will be used.
• Original Context: The portion of the response URL containing the target.

Example Scenario: Session IDs

A typical situation using dynamic targets is load testing an application that provides a unique session ID for each user. In this scenario, the session ID dynamic target may appear in the Dynamic Targets view.

The step whose number appears in the From column will include the dynamic target in its response. Here, it appears in the headers.

The step whose number appears in the To column will include the dynamic target in its request. A special section appears in the Request tab indicating that this response is bound to a dynamic target.

Custom Dynamic Targets

Based on the HTTP traffic there might be targets which are not detected by Test Studio as dynamic but still these will be required to accomplish meaningful scenario. Or any of the auto-detected dynamic targets is not listed for transfer to a desired request. To handle such scenarios Test Studio implemented the ability to add Custom Dynamic Targets.

• Add Custom Dynamic Target
• Source Section Properties
• Search Options In Source Step Respponse
• Destination Section Properties
• Append Custom Text to Dynamic Value
• Important Notes

Add Custom Dynamic Target

The Custom Dynamic Targets are available in the Choose Dynamic Targets view where all auto-detected are listed as well - once a user profile is captured or opened to be modified click the Choose Dynamic Targets button.

Once any custom targets are added to the user profile these will be displayed under the list with all auto-detected dynamic targets. To add a custom dynamic target use the Add Dynamic Target button.

See Also: A sample scenario to cover with the help of custom dynamic targets is described in our blog post Custom Dynamic Targets in Load Tests.

Source Section Properties

• Step: Step to take the target from. Any step which contains a HTTP request can be selected. The Think time steps are filtered out and not displayed in the dropdown.
• Response: Which part of the HTTP response to be used - Body, Headers or Cookie. Select the necessary part of the HTTP response and verify its content.
• Content: Displays the content of the selected response part.
• Search Type: The type of search to be used in the content of the selected response - FullText, Regex, JSON, XML. Select any of the provided options to search for the necessary value from the response.
• Starts after/before|Regex|JSON path|XPath: Provide the search query to locate the desired value in the response.
• Search Result: Click to show the result based on the search query.
• Current Value: Display the current result based on the search query.

Source Body	Source Headers
Source Cookie

Search Options

• FullText - use strings which surround the desired value to locate it in response.

Example: The head section of a HTTP response's body is:

<html>
<head><title>Example ASP Scripts</title></head>

To get the actual title you may use Starts after: <title> and Ends before: </title>

• Regex - use regular expression to locate the desired value in response body, header or cookie.

Note! Test Studio uses <val> to express the first match in response!

Example: The cookie of a HTTP response is the following string and the requirement is to get the domain name value only:

_EDGE_S=SID=04D5974D8509631807D39B2484BF62E4; path=/; httponly; domain=bing.com

The only possible approach is to use the partial search using Regex. The standard regex for extracting the desired value looks like this:

domain=(.*?)$

This returns the following match information:

Full match  65-80   `domain=bing.com`
Group 1.    72-80   `bing.com`

Using that standard regular expression in Test Studio will return the Full match instead the value in Group 1. Therefore Test Studio uses <val> to express the first match group and the regular expression becomes:

domain=(?<val>.*?)$

• JSON - use JSONPath to locate the desired value in response.

• _XML - use XPath to locate the desired value in response.

Destination Section Properties

• Step: Step to pass the target to. Any step, that follows the selected one for source and contains a HTTP request, could be selected for destination step. The Think time steps are filtered out and not displayed in the dropdown.
• Field Type: In which part of the HTTP request to include the dynamic value - Query Paramater, Header, Cookie, POST data, URL.
• Field Name: The name of the dynamic target which will be used in the HTTP request - particular query parameter, header, or cookie.

Append Custom Text to Dynamic Value

In some cases the dynamic parameter is built by a value from any previous HTTP response and a predefined static text - an example of such implementation could be an authorization header for some applications. The expected header in this occasion consists of predefined and known text, which either precedes and/or follows the dynamic part, and the dynamic value extracted from a previous response.

In Test Studio load module you can create such dynamic target using the available append options allowed in the Destination section's Field Name text box. All of these use the following template, where Prefix and Suffix are optional:

Query Parameter, Cookie, Header
'ParamName:Prefix{value}Suffix'

URL
'Prefix{value}Suffix'

Note! Keep in mind that blank spaces in the Field Name text box are considered valid character and thus are included in the final string. Therefore, leave intervals in the text only if these are expected.

• Query Parameter - list the name of the query parameter as it will be listed in the URL, the predefined text and set the value extracted from the source step in curly brackets.
  • Ex.: source:search-for-{value} - if the extracted value is test, the query parameter will be appended as source=search-for-test.
  • Ex.: source:{value}searching - if the extracted value is test, the query parameter will be appended as source=testsearching.
• Header - list the name of the header to replace followed by colon (:), the predefined text and set the value extracted from the source step in curly brackets.
  • Ex.: Authorization:TOKEN-{value} - if the extracted value is test, the Authorization header will be appended as TOKEN-test.
  • Ex.: Authorization:{value} AuthToken - if the extracted value is test, the Authorization header will be appended as test AuthToken.
• Cookie - list the name of the cookie to replace followed by colon (:), the predefined text and set the value extracted from the source step in curly brackets.
  • Ex.: SessionID:currSession-{value} - if the extracted value is test, the SessionID cookie will be appended as currSession-test.
  • Ex.: SessionID:currSession-{value} SID - if the extracted value is test, the SessionID cookie will be appended as currSession-test SID.
• URL - list the redirect URL as it need to be sent to the server, the predefined text and set the value extracted from the source step in curly brackets.
  • Ex.: http://google.com/{value} - if the extracted value is test, the URL will be appended as http://google.com/test.
  • Ex.: http://google.com/{value}/id=1379 - if the extracted value is test, the URL will be appended as http://google.com/test/id=1379.

Append Query Parameter	Append Header
Append Cookie	Append URL

Note! The above examples only represent how to append some predefined text before or after the dynamic value for the different types of destination fields. These are no real example of working HTTP calls.

Important Notes

Note! The custom dynamic value will be added to the destination HTTP request even if there is no such parameter, cookie or header existing in the recorded request.
Note! If there are both autodetected and custom dynamic values for a single destination step, the last set target will be used in the request. Disable/Enable of a dynamic target will update the order of set targets.
Note! As of now there is no visual representation for any custom dynamic targets within the Edit User Profile view. To verify if the HTTP requests are built as you expect you could use Fiddler to capture the traffic of a sample load test execution and inspect these.