Section 6: Mox Coffee - Mid Sec Work

[Jon-Mervedel]

Hello all!

I took a few days to give myself a refresher in Python and am now back to the course.

I have a question concerning my logic of the workshop. When the following code is given these are the results:

SEND_VALUE = to_wei(1, "ether")
RANDOM_USER = boa.env.generate_address("non-owner")

def test_can_withdraw_from_multiple_users(coffee):
    for i in range(10):
        with boa.env.prank(RANDOM_USER):
            boa.env.set_balance(RANDOM_USER, SEND_VALUE)
            coffee.fund(value=SEND_VALUE)
    assert boa.env.get_balance(coffee.address) == to_wei(10, "ether") 

    with boa.env.prank(coffee.OWNER()): 
        withdrawal = coffee.withdraw()

    assert boa.env.get_balance(coffee.address) == 0 

1 passed, 6 deselected in 0.10s

However, when the following is added there is a problem:

--snip--
assert boa.env.get_balance(coffee.OWNER()) == withdrawal

And the following error:

>       assert boa.env.get_balance(coffee.OWNER()) == withdrawal
E       AssertionError

tests/unit/test_unit_coffee.py:68: AssertionError
====================================== short test summary info===============================
FAILED tests/unit/test_unit_coffee.py::test_can_withdraw_from_multiple_users - AssertionError
1 failed, 6 deselected in 0.46s 

What am I possibly doing to cause the error? I know it has to be coming from the added assertion, but can not solve what it may be. I also know its probably a simple error I'm making.

Any help is appreciated!

[EngrPips]

Hello @Jon-Mervedel, below is the withdrawal function of my buy_me_a_coffee contract.

@external
def withdraw():
    self._only_owner()
    for funder: address in self.funders:
        self.address_to_amount_funded[funder] = 0
    self.funders = []
    # send(OWNER, self.balance)
    raw_call(OWNER, b"", value = self.balance)

So if you have the same withdrawal function as me, then it makes sense that the test fails because this withdrawal function basically doesn't return any value. So when you try to store the returned value from calling the function as shown below, you will basically be storing 0

withdrawal = coffee.withdraw()

Obviously, you have withdrawn the balance of the contract to the owner with the line of code above, but when you do the assertion below, you will be comparing 0 to a non 0 value which causes the assertion to error out, and the test will fail.

assert boa.env.get_balance(coffee.OWNER()) // this will return the actual balance of owner (!0) == withdrawal // this is `0` because the `withdraw` function of the `buy_me_a_coffee` does not return any value.

I hope I did justice to this explanation. Please ask questions if anything is still unclear

[Jon-Mervedel]

I think I got it... lol

I needed to set OWNER blance to "0" first.

SEND_VALUE = to_wei(1, "ether")
RANDOM_USER = boa.env.generate_address("non-owner")


def test_can_withdraw_from_multiple_users(coffee):
    total = 0
    for i in range(10):
        with boa.env.prank(RANDOM_USER):                
            boa.env.set_balance(RANDOM_USER, SEND_VALUE)
            coffee.fund(value=SEND_VALUE)
            total += SEND_VALUE     
    assert boa.env.get_balance(coffee.address) == total 

    with boa.env.prank(coffee.OWNER()): 
        boa.env.set_balance(coffee.OWNER(), 0)
        coffee.withdraw()
    assert boa.env.get_balance(coffee.address) == 0 
    assert boa.env.get_balance(coffee.OWNER())  == total 

test result:
= 1 passed, 6 deselected in 0.13s =

conftest file

import pytest
from script.deploy import deploy_coffee
from script.deploy_mocks import deploy_feed
from moccasin.config import get_active_network
import boa



@pytest.fixture(scope="session")
def account():
    return get_active_network().get_default_account()



@pytest.fixture(scope="session")
def eth_usd():
    return deploy_feed()



@pytest.fixture(scope="function") 
def coffee(eth_usd):
    return deploy_coffee(eth_usd)

[EngrPips]

How come the owner has that crazy amount at first? Is that just some default amount funded to all addresses?

[Jon-Mervedel]

I have no idea. That is a good question though, because it should be empty.

I think when I finish this course, I will retake it, to shore up any places that I may be weak in.

It all depends on what's expected of me at the end compared to what I feel that I can competently do.

[EngrPips]

Yeah, The second time will be easier than the first.

[Jon-Mervedel]

Exactly, friend!

[Jon-Mervedel]

For OWNER with previous funds in account without resetting the balance:

edit:

SEND_VALUE = to_wei(1, "ether")
RANDOM_USER = boa.env.generate_address("non-owner")

def test_can_withdraw_from_multiple_users(coffee):
    funded = 0
    for i in range(10):
        with boa.env.prank(RANDOM_USER):                    
            boa.env.set_balance(RANDOM_USER, SEND_VALUE)
            coffee.fund(value=SEND_VALUE)
            funded += SEND_VALUE
    assert funded == boa.env.get_balance(coffee.address)

    with boa.env.prank(coffee.OWNER()): 
        original_balance = boa.env.get_balance(coffee.OWNER())
        coffee.withdraw()       
    assert ) boa.env.get_balance(coffee.address) == 0 
    assert  original_balance + funded == boa.env.get_balance(coffee.OWNER())

[EngrPips]

I am not sure what you intend with this.

[Jon-Mervedel]

I am unclear of what you mean?

The last code I published is the code if the owner has funds in the account.

Previously I set the balance to "0" wiping out ETH because I thought the project consisted of taking a new account and funding it with 10 funders. However the pranked account came pre-loaded so withdrawing was == 10 eth, but owner's balance += withdrawal.

I was originally asserting the owner's balance was now 10 eth.

[EngrPips]

Interesting, This makes sense