Lesson 9. Trying to use assert.approximately

[NickoMenty]

I am trying to check the sum amount after the raffle, and it seems that it takes some sort of fee that I am lacking.
And I am trying to use assert.approximately, but i don't understand why it doesn't work

raffleEntranceFee = await raffle.getEntranceFee()
const winnerEndingBalance = Number( await ethers.provider.getBalance(accounts[1]), )
const winnerStartingBalance = Number( await ethers.provider.getBalance(accounts[1]), )


assert.approximately( winnerEndingBalance, winnerStartingBalance + Number(raffleEntranceFee) * additionalEntrants + Number(raffleEntranceFee), 0.001, )

My 0.001 delta is big enough to manage this difference. however I still receive an error:

AssertionError: expected 1.0001999618434436e+22 to be close to 1.0001999705007882e+22 +/- 0.001

[Nlferu]

@NickoMenty

Much better way to test this will be adding gas cost calculation and deducting those from proper balance :)

You can calculate exact transaction cost like below:

let txReceipt = await txResponse.wait()

const gas = txReceipt.gasUsed
const gasPrice = txReceipt.effectiveGasPrice
const gasCost = gas.mul(newGasPrice)

[NickoMenty]

hi, thank you. But this is complex funciton that has gas fee for deposeting, withdrawing, receiveng random number, etc.
Then I would need to calculate all these gasFees and deduct them all. It seems much easier to understand how assert.approximately works.
I mean for me :D

[Nlferu]

@NickoMenty

It is not complex trust me :) you just indeed have to calculate gas cost for each function call that is not view function, but you do it as simple as I showed you. Unfortunately I didnt play with approximately assertions as those are not so accurate, but it can be messing with amounts formats, which are converting from floats/strings etc. so I would check returns if those are summing up correctly by simply adding console.log with all data you are checking -> you can then estimate if your calculations are good etc.

[NickoMenty]

Hi, okay, thank you, I will give it a try!)

[Nlferu]

Let me know if it was helpful, but from my experience console.log's are best friends in such tests :D