What is the proper way to do load testing for node.js backend which uses firebase onCall functions and redis?

We are trying to make a load testing script in node, in order to test our back-end. We are using on.call firebase functions and redis.

The system is composed by mobile devices, which will send coordinates and move continuously, hitting the on.call firebase functions which in turn interact with firebase database and redis.

Which would be the proper way to do it? we would like to make thousands of instances which will send data and move continuously.

We were thinking of experimental workers or web workers in order to make threads to emulate each device.