Load Testing: Logic Controllers in JMeter (Transaction, ForEach, If)

A simple way to describe JMeter is a tool that captures the way your web application interacts with the web and assesses performance of your web application. Like other testing tools, it has steps that in a combination carry out a particular test. JMeter offers logic controllers to group your steps so that you can ascertain the way the steps behave. One you get along with JMeter, using some of those logic controllers will be inevitable. Here I will try to show how to use some of the logic controllers I often use.

1.    Transaction Controller: This helps you to group steps. Suppose you want to assess the performance of a successful login action. And a successful login action requires more than one HTTP requests. So you can group them in a transaction controller as shown below.

Then add a Summary Report listener to the thread group. Now if you run the test you will notice that a separate assessment is being shown for transaction controller.

2.    ForEach Controller: ForEach controllers are very helpful to loop through an array. Suppose, you are visiting a page that contains a list of some objects. You want to delete some objects with names having a common prefix. And the delete operation requires ID of an object being deleted. Now you can do the followings:

a.    Identify the HTTP request that loads list of the objects. Add a Regular expression extractor (post processors) that extracts IDs of the objects you want to delete. You can configure the extractor as shown below

1.       Give a  name of the variable/array

2.       Enter regular expression that extracts the ID

3.       Add template to refer to group 1 within the regular expression

4.       Add -1 to consider all values returned by the regular expression

5.       Add a default value of the variable

b.      Add ForEach controller and place the delete step within as shown below

1.       Give the reference name of previous step as ‘Input variable prefix’ here

2.       Enter an ‘Output variable name’. This variable will be referred in delete step.

c.       Refer to the ‘Output variable name’ as given above in delete step as shown below

If you run the test now, you will notice that the steps mentioned under ForEach Controller is executed as many times as the IDs the regular expression extractor returns. You can check this in a View Results Tree listener.

3.     If Controller: As the name suggests, it allows you to apply if else condition to your tests. Suppose you have two different sets of steps to create two different types of users. And you want your test to decide which set of steps to execute depending on the value of a variable. You can do the followings

a.    Group the sets of steps as mentioned above in two different If Controllers. And add a ‘User Defined Variables’ config element as shown below

b.    Configure the If Controller  as shown below

Here the Condition asks If Controller to execute the steps only if value of the variable is "Type 1". Similarly you can configure the 2^nd If Controller as shown below.

I will show how to use  the following controllers in my next post

• Include Controller
• Interleave Controller
• Loop Controller
• Module Controller
• Once Only Controller