tell me how to correctly and better test eventEmitter for the number of listeners

I have a function that connects listeners to events, the number of listeners depends on the number of packets arriving in this function.

The essence of the test is to make sure that the number of packets is equal to the number of listeners, The test is written in JEST.

if you need any more screenshots, write and I'll add everything.

https://ibb.co/wN3fDbw - link to screenshot.