Add a way to capture events values to be able to write tests requiring them

[bhuisgen]

As the issue #581, I need an easy way to capture values from event to reuse them.

For the moment and thanks to @wminshew I did this:

  it('should burn tokens if asked', async () => {
    const response = await (
      await contract.safeMint(await owner.getAddress())
    ).wait();

    expect(response.events[0].event).to.equals('Transfer');
    const [, , tokenId] = response.events.[0].args;

    await expect(await contract.burn(tokenId)).to.emit(contract, 'Transfer');
  });

Note the boring stuff about response / await / await / wait and the required expect on the event name. Maybe something like that could be interesting:

const args = await expect(await contract.safeMint(await owner.getAddress())).to.emit(contract, 'Transfer').args();
const tokenId = args[2];

[rzadp]

Interesting, wondering what we would like to return in the case of chaining the matcher, ie:

await expect(tx)
  .to.emit(contract, 'Transfer')
  .to.emit(contract, 'Mint')
  .args()

Just the arguments of the last one, Mint? Have you thought about this, what would make sense to you in this case?

[bhuisgen]

Yes, it would be perfect ie args() returning the values of the event from the last emit().