Lesson 9: Why is gas not added to the ending balance when comparing with assert

[ghost]

In the hardhat-fund-me unit tests we compared starting balance and ending balance like this:
Fund-Me

assert.equal(
    startingDeployerBalance.add(startingFundMeBalance).toString(),
    endingDeployerBalance.add(gasCost).toString()
)

But now we don't care about gas cost, why?
Raffle

assert.equal(
    winnerEndingBalance.toString(),
    winnerStartingBalance.add(raffleEntranceFee).toString()
)

[krakxn]

Going by sheer memory here, but pretty sure raffleEntranceFee is inclusive of gas fees. If this is not the case, let me know

[krakxn]

@woojiq

assert.equal(
                                  winnerBalance.toString(),
                                  startingBalance
                                      .add(
                                          raffleEntranceFee
                                              .mul(additionalEntrances)
                                              .add(raffleEntranceFee)
                                      )
                                      .toString()
                              )

Is this the relevant code from staging tests you are referring to?

[ghost]

yes, this is one of many examples

[krakxn]

I did not see any gas compensations in the staging test -- only this. Could you paste specifically the code where we do, which you are referring to?

If it is this one, we are not taking gas in consideration here.

[ghost]

The problem is precisely that in this project we do not care about gas, but in lesson 7 - Fune-Me smart contract we care about it. Here is a link to a line of code: https://github.com/PatrickAlphaC/hardhat-fund-me-fcc/blob/5f58a1c4690929b775c53b2abab9b41f58f294e7/test/unit/FundMe.test.js#L123

[krakxn]

Got it, @alymurtazamemon gave a solution already though -- you should read his'.

[hobbescodes]

@woojiq In the Fund Me contract, the deployer, or owner, is the one to call the withdraw function and therefore has to pay the gas fees in order to call that function. In the Raffle contract, the funds are transferred internally through the fulfillRandomWords function, therefore the winner is never submitting a transaction to withdraw the funds. Hence, why you do not need to calculate gasCost when comparing winnerStartingBalance and winnerEndingBalance.

[ghost]

Yes, I understand, thx. But marked answer is more clear as for me.

[alymurtazamemon]

@woojiq In the fund me contract, the deployer account was calling a withdraw function and that's why gas was deducted from the deployer account. But in the raffle case, fulfillRandomWords was called by the Chainlink node and we already paid them a fee for it. That calling triggered the event and we select the winner, so the fee was never deducted from the winner's account that's why we did not calculate like the fund me contract.

Hope it clears your query.

[srikarsams]

@alymurtazamemon But when we fund the smart contract with 0.1ETH, we'll be spending some gas fees. Isn't it? Am I missing something? Don't we need to add it to startingBalance?

[ManuWeb3]

@srikarsams ... if you carefully notice the order of the code in unit-testing fulfillRandomWords(), we first executed enterRaffle() by all the additional players (this is where gas got spent by every player and deducted from their actual starting balance) and after this we retrieved the balance in the variable startingBalance which is not the actual starting Balance of winner (an additional player[2], in this case).

for (let i = startingIndex; i < startingIndex + additionalEntrances; i++) { // i = 2; i < 5; i=i+1
                      raffle = raffleContract.connect(accounts[i]) // Returns a new instance of the Raffle contract connected to player
                      await raffle.enterRaffle({ value: raffleEntranceFee })
                  }

After the above code, below runs:

const tx = await raffle.performUpkeep("0x")
                      const txReceipt = await tx.wait(1)
                      const startingBalance = await accounts[2].getBalance()

This means the startingBalance in the above code is excluded of the gasCost (as it already got spent earlier during enterRaffle) So, you don't need to add the gasCost back unlike you did in FundMe.sol

Hope, I could clarify this.