Periodically when implementing advanced JMeter test scenarios, you may need to build a JMeter Variable from two or more other variables. This short post will look at how to do just that.

These test scenarios might originate from a Counter Test Element or Function, the __threadNum()function, a regular expression resulting in multiple matches or perhaps a different need.

Let’s imagine the following situation:

There are 2 JMeter Variables:

1. myVar_1 with the value of foo
2. myVar_2 with the value of bar

There is also a Counter test element with the reference name of counter.

The objective is to have a dynamic combined variable which consists of:

• Prefix: myVar_
• Postfix: ${counter} variable value that is dynamic

The solution is using the __V() function which can be used to evaluate composite variables.

The syntax is:

${__V(PREFIX${POSTFIX})}

In the case above, the resulting composite variable reference would be:

${__V(myVar_${counter})}

See how to do this in the image below.

One More Hint

If you build a data-driven test and have parameters in a file that you’re reading by using the__StringFromFile() or __FileToString() functions, and the file has JMeter Variables which need to be substituted with the corresponding values in runtime - you need to use the __eval() function so that the variable value could be resolved.

Looking for More Info on JMeter Functions?

For more information on the above and other useful JMeter Functions check out the following articles:

• Using JMeter Functions - Part I
• Using JMeter Functions - Part II
• How to Use JMeter Functions - Part III