Mastering Data Looping in JMeter: A Simple Trick for Efficient Testing

In this blog post, we are going to see a simple trick in JMeter which will loop through all the data in JMeter. This is particularly helpful to test the APIs or web transactions where it needs to execute at least once.

Table of Contents

Problem Statement

By default, JMeter won’t loop through all the test data from the CSV test data element.


Consider a web application like where there is a requirement to add all the products one by one to check out. Below are the product IDs in a CSV file in the current directory where the JMeter test plan resides.

CSV Test Data - Mastering Data Looping in JMeter: A Simple Trick for Efficient Testing

The following are the properties of the CSV Test Data Config element.

CSV Data Set Config

When we run this test plan with the Loop Count as -1 in the Thread Group, below is the output. To ensure that all test data is sent in the request, set the Recycle on EOF property of the CSV Data Set Config to False and the Stop Thread on EOF property to True.

The issue with this approach is that people often overlook the potential problem of misconfigurations in the Thread Group or the CSV Data Set Config properties.

To avoid this, adding one more layer to validate will be helpful i.e. adding If Controller with the below statement will check for <EOF>. If there is an error, it will stop the execution, regardless of the settings in CSV Data Set Config, such as Recycle on EOF.

${__groovy(vars.get("PRODUCT_ID") != "<EOF>",)}

This will yield the same output as above, but with an extra layer of confidence.


In conclusion, mastering the power of JMeter’s data looping is akin to wielding a finely-tuned instrument in the grand orchestra of performance testing. By implementing the simple yet ingenious trick of using an If Controller with a Groovy assertion, we sidestep the pitfalls of overlooked configurations and ensure our test plans are both robust and fail-safe. Embrace this method, and you will elevate your testing suite to a new level of precision and reliability. Remember, in the realm of API and web transaction testing, it’s the small nuances that make all the difference. Test smart, not hard, and let JMeter’s full potential unfold under your command. Happy testing

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