Lesson 7: SmartContract Lottery (updated test_can_pick_winner_correctly)

[SJ50]

Hi all,
I have created better version of test_can_pick_winner_correctly test.

• This code does not uses random no of account to participate
• prevents deployer/owner account ( account() ) to participate in lottery

Any feedback are welcome.

def test_can_pick_winner_correctly():
    # Arrange
    if network.show_active() not in LOCAL_BLOCKCHAIN_ENVIRONMENTS:
        pytest.skip()
    lottery = deploy_lottery()
    account = get_account()
    entrance_fee = lottery.getEntranceFee()
    random_int = random.randint(10**18, 10**19)
    random_no_for_participant_account = random.randint(2, 9)
    index_of_participant_account = range(1, random_no_for_participant_account)
    random_winner_account_index = (random_int % len(index_of_participant_account)) + 1
    print(random_winner_account_index)

    lottery.startLottery({"from": account})
    for i in index_of_participant_account:
        lottery.enter({"from": get_account(index=i), "value": entrance_fee})

    fund_with_link(lottery.address)
    account_balance_after_entry = get_account(
        index=(random_winner_account_index)
    ).balance()
    balance_of_lottery = lottery.balance()
    tx = lottery.endLottery({"from": account})
    request_id = tx.events["RequestedRandomness"]["requestId"]

    # Act
    get_contract("vrf_coordinator").callBackWithRandomness(
        request_id, random_int, lottery.address, {"from": account}
    )
    # Assert

    assert lottery.recentWinner() == get_account(index=random_winner_account_index)
    assert lottery.balance() == 0
    assert (
        get_account(index=random_winner_account_index).balance()
        == account_balance_after_entry + balance_of_lottery
    )

[cromewar]

Hello @SJ50
This is really good for testing purposes as you just want to have a quick feedback about the winner of the lottery, how ever take in mind that randint generates a pseudo random number, which just takes a space of memory but is no actually random. So, for projects deployed into de mainnet is better to use VRF from chainlink to get a truly random number.

Cheers.

[SJ50]

I understand your point, but I am new to python and solidity, so this is good start for me.
I have to go through whole course again, before I understand it completely.

[cromewar]

You are doing great, this is an advanced test and you manage to it 100% for yourself, fell free to make any other questions here.
Cheers.