Lesson 9: How to get requestId from VRFCoordinatorV2Mock RandomWordsRequested event

[emilianolch]

As Patrick suggested in performUpkeep unit testing, there's no need to emit an event here because VRFCoordinator already emits one when a random number is requested. So, I got rid of RequestedRaffleWinner event in Raffle contract. But then I ran into an issue when I tried to get the requestId in the test. It seems that when the event doesn't come from the contrarct that initiated the transaction, the event data is not parsed, hence you can't access to args.

If you wanted to get requestId this way:
const requestId = txReceipt.events[0].args.requestId;

you'll get this error:
TypeError: Cannot read properties of undefined (reading 'requestId')

In order to be able to get requestId from VRFCoordinator event you should do this:
const requestId = vrfCoordinatorMock.interface.parseLog( txReceipt.events[0] ).args.requestId;

[jtsaich]

Awesome, this is great!