Lesson 09: Unit testing: fulfillRandomWords() - few questions

[ManuWeb3]

Hi everyone,

Runnig the unit test below, I observed that all 3 new instances of Raffle.sol created inside for loop are deployed at the same address, terminal snip attached at the end.

As ethers.js says, contract.connect( providerOrSigner ) ⇒ Contract returns a new instance of the Contract.

1. Shouldn't the addresses be different if 3 new instances of Raffle.sol are getting created?

I added console.log(`Address of new Raffle_instance: ${accountConnectedRaffle.address}`) and saw this.

2. Secondly, these 3 new instances act on behalf of new signer i.e. accounts[i].

When these new instances are connected to different accounts[i], how come these accounts[i] got included and dealt with in the raffle variable that we got from the originally deployed Raffle.sol (in the first beforeEach block) via raffle = await ethers.getContract("Raffle", deployer)

I mean, I'm not able to wrap my head around how we are only calling the functions using raffle variable like const raffleState = await raffle.getRaffleState() inside try{ } block when we have 3 new instances of the contract, that too connected to 3 different accounts[i].

Isn't raffle abstraction only connected with 1 account and that's deployer ?

How could we select winner when all the 4 instances are connected to different accounts[i] (including the deployer)

Tried my best to convey my concern but if it's still unclear, sorry, I can try rephrasing. Let me know please.

!developmentChains.includes(network.name) ? describe.skip : describe("Raffle", function () {

    let raffle, vrfCoordinatorV2Mock, raffleEntranceFee, deployer, interval
    const chainId = network.config.chainId

    beforeEach(async function() {
    deployer = (await getNamedAccounts()).deployer          
    await deployments.fixture(["all"])
    raffle = await ethers.getContract("Raffle", deployer)
    console.log(`Address of original Raffle_instance in beforeEach# 1:  ${raffle.address}`)
    vrfCoordinatorV2Mock = await ethers.getContract("VRFCoordinatorV2Mock", deployer) 
    raffleEntranceFee = await raffle.getEntranceFee()
    interval = await raffle.getInterval()
 })

describe ("fulfillRandomWords", function (){

beforeEach(async function(){
            
            await raffle.enterRaffle({value: raffleEntranceFee})
            await network.provider.send("evm_increaseTime", [interval.toNumber() + 1])
            await network.provider.send("evm_mine", [])
        })

it("Should pick up a random Winner, resets the Lottery, and sends the money to the Winner.", async function(){
            const additionalEntrants = 3                    
            const startingAccountIndex = 1
            const accounts = await ethers.getSigners()

for (let i=startingAccountIndex; i < startingAccountIndex + additionalEntrants; i++) {
                const accountConnectedRaffle = raffle.connect(accounts[i])
                //  checking all addresses for clarity...
                console.log(`Address of new Raffle_instance: ${accountConnectedRaffle.address}`)
                await accountConnectedRaffle.enterRaffle({value: raffleEntranceFee})
            }

const startingTimestamp = await raffle.getLatestTimestamp()

                await new Promise(async (resolve, reject) => {                  
                raffle.once("WinnerPicked", async () => {                   
                                                                    
                console.log("Found the emitted event - Winner Picked")

              try {
                    const recentWinner = await raffle.getRecentWinner()
                    console.log(`Recent Winner            : ${recentWinner}`)
                    console.log(`Deployer                  : ${deployer}`)
                    console.log(`AdditionalEntrant# 1   : ${accounts[1].address}`)      
                    console.log(`AdditionalEntrant# 2   : ${accounts[2].address}`)
                    console.log(`AdditionalEntrant# 3   : ${accounts[3].address}`)

                    //  testing 3 variables that should be reset by now
                    const raffleState = await raffle.getRaffleState()
                    const numPlayers = await raffle.getNumOfPlayers()
                    const endingTimestamp = await raffle.getLatestTimestamp()           

                    // assert statements to check all 3
                    assert.equal(raffleState.toString(), "0")
                    assert.equal(numPlayers.toString(), "0")                            
                    assert(endingTimestamp > startingTimestamp)

                } catch(e) {
                    reject(e)                                           
                } 
                resolve()                                             

                })

                const tx = await raffle.performUpkeep([])               
                const txReceipt = await tx.wait(1)                     
                await vrfCoordinatorV2Mock.fulfillRandomWords(txReceipt.events[1].args.requestId, raffle.address)

                })
            })
        })

3. Also, why am I always getting the same account as the winner if the selection is random. I've run the test 8 times.
Is it because it's a local development network of HH?

So much so, even Patrick got the same winner.

Thanks

[adityabhattad2021]

Based on my understanding to your questions

1. How could we select winner when all the 4 instances are connected to different accounts[i] (including the deployer)
   => Multiple users are connected to same contract at a same time
   In here

for (let i=startingAccountIndex; i < startingAccountIndex + additionalEntrants; i++) {
                const accountConnectedRaffle = raffle.connect(accounts[i])
                //  checking all addresses for clarity...
                console.log(`Address of new Raffle_instance: ${accountConnectedRaffle.address}`)
                await accountConnectedRaffle.enterRaffle({value: raffleEntranceFee})
            }

We are simply connecting the same contract with different accounts which is evident as with this line:

console.log(`Address of new Raffle_instance: ${accountConnectedRaffle.address}`)

you are getting address of same contract.
With this line

await accountConnectedRaffle.enterRaffle({value: raffleEntranceFee})

we are making a transection from the same contract which is currently connected to account[i] (i being 0,1,2,3) and with next iteration of the loop connecting to the next account and repeating the process again.

2. Also, why am I always getting the same account as the winner if the selection is random. I've run the test 8 times.
   Is it because it's a local development network of HH?
   => You are getting the same account as winner VRFCoordinatorV2Mock.sol is providing the same random number as it is only meant for testing purpose. You see on real network VRFCoordinatorV2 will need some computational power for generating a random number which require LINK tokens.

Tried my best to explain.
Hope it helps!

[alymurtazamemon]

@adityabhattad2021 explains well, here I am going to explain my way.

Your first question:

Q1. Shouldn't the addresses be different if 3 new instances of Raffle.sol are getting created?

Ans: Raffle instance is not created again, it is only created once when we run this command in the beforeEach block, this line deployed Raffle and Mocks:

await deployments.fixture(["all"]);

Now we get those deployed contracts with the help of hardhat ether and connect it deployer, like this:

raffle = await ethers.getContract("Raffle", deployer)

Now, anything we do with the contract, msg.sender will be the deployer account.

Now, I am not able to understand your second question properly, sorry for that, but I am going to explain it further so it will make sense to you.

So now we want to test that when multiple players enter into the raffle, our contract should select the winner and transfer the amount to him/her. For that, the first requirement is to enter multiple players into the raffle, right? But if we directly call the enterRaffle function the msg.sender will be our deployer account (as I mentioned above). For that reason, we want to change our msg.sender of a contract to different accounts (players accounts), these lines is doing that:

const accountConnectedRaffle = raffle.connect(accounts[i])
await accountConnectedRaffle.enterRaffle({value: raffleEntranceFee})

The first line is connecting our contract with other players' accounts (in every iteration of the loop), so the msg.sender of the contract should be other players' accounts and not the deployer account.

And the second line is calling enterRaffle function based on the player account address.

This way we achieved what we wanted to enter multiple players into the raffle contract, further in the test we select a winner and send money to the winner's account simply.

Hope it helps you understand the process.

[ManuWeb3]

Thanks @alymurtazamemon and @adityabhattad2021 for taking this up.

The root cause of my "multiple instances got created" doubt is the ethers.js documentation below:

It says, contract.connect() returns new instance of the contract.

That's what led me to think that const accountConnectedRaffle = raffle.connect(accounts[i]) is returning a new instance in every iteration

So, am I misunderstanding the ether.js documentation ?

[adityabhattad2021]

Happy Coding :)

[alymurtazamemon]

@ManuWeb3 No, your understanding is correct. And we made a mistake here that I am going to correct.

As I said above no new instance was created because you asked why they all have the same address. Actually, I must had say that it is not deploying again, but with every iteration, it creates a new copy of a smart contract with the new signer (like they used the language in the doc).

[adityabhattad2021]

@alymurtazamemon can you please correct my analogy.

[alymurtazamemon]

@adityabhattad2021 Your analogy is already correct.

[ManuWeb3]

Thank you @alymurtazamemon for taking the time to provide more clarification.