Triggered task - how to store data passed in querry parameter in a variable

I have created pipeline with parameter as test and created triggered task which is invoking pipeline

I am calling that task using below URL
https://elastic.snaplogic.com:443/api/1/rest/slsched/feed/StanfordDev/projects/gsb/test?test=jayr

How can i store value of querry parameter in a variable like “test”
I can access parameter by using ${_test} but not able to store it using mapper

prefix your pipeline parameter with and underscore “_” (e.g. _test)

Thanks @aleung . It worked