How can I check if my Webservice is working with Runscope and random strings?

I have a very basic check if my webservice is still up and running by sending a query to my-endpoint.com?heartbeat={{utc_datetime}}. The service simply returns the value of heartbeat.

However, if I set the Assertion

Text Body equals {{utc_datetime}}

this fails, as it is a few milliseconds different. How can I use the same variable that was send on http://runscope.com?

Create an Initial Variable (expand the Environment settings at the top of the test editor) with a name like date and a value of {{utc_datetime}}. That will create a static value you can reference throughout the test using {{date}}.