## Mock Contracts To test our smart contracts, we are going to deploy mock versions of them to our own local PyEVM network. First, we need to make a script to deploy our own fake price feed contract. To deploy our own fake price feed contract, we will need to grab the code from the Chainlink GitHub repo. We can find the code in the `src/mocks/mock_v3_aggregator.vy` file. We will copy and paste the code into our project, and will need to convert it from Solidity to Vyper. We have a minimal Chainlink price feed contract here in Vyper. We are going to use this for mocking, not for actually deploying price feeds. We have created a new script called `deploy_mocks.py`. This script will deploy our mock price feed contract. ```python from src.mocks import mock_v3_aggregator from moccasin.boa.tools import VyperContract STARTING_DECIMALS = 8 STARTING_PRICE = int(2000e8) def deploy_feed() -> VyperContract: return mock_v3_aggregator.deploy(STARTING_DECIMALS, STARTING_PRICE) def moccasin_main(): active_network = get_active_network() price_feed: VyperContract = deploy_feed() coffee = buy_me_a_coffee.deploy(price_feed.address) print(f"Coffee deployed at: {coffee.address}") print(coffee.get_eth_to_usd_rate(1000)) ``` We also have a `deploy.py` script to run these contracts. ```python from moccasin.config import get_active_network from script.deploy_mocks import deploy_feed from moccasin.boa.tools import VyperContract from src import buy_me_a_coffee def deploy_coffee(price_feed: str): buy_me_a_coffee.deploy(price_feed) def moccasin_main(): active_network = get_active_network() price_feed: VyperContract = deploy_feed() coffee = buy_me_a_coffee.deploy(price_feed.address) print(f"Coffee deployed at: {coffee.address}") coffee.get_eth_to_usd_rate(1000) ``` This method of mocking is common in testing. We might need to rewrite a contract to make it easier to work with. **Code Block for `mock_v3_aggregator.vy`:** ```python # pragma version 0.4.1 #license MIT DECIMALS: immutable(uint8) latestAnswer: public(int256) latestTimestamp: public(uint256) latestRound: public(uint256) getAnswer: public(HashMap[uint256, int256]) getTimestamp: public(HashMap[uint256, uint256]) getStartedAt: public(HashMap[uint256, uint256]) supply: uint256 decimals: uint256 version: public(constant(uint256)) = 4 @deploy def __init__(decimals: uint8, initialAnswer: int256): DECIMALS = decimals self.updateAnswer(initialAnswer) print(f"HELLO FROM MOCK AGGREGATOR") @internal def updateAnswer(answer: int256): self.latestAnswer = answer self.latestTimestamp = block.timestamp self.latestRound = self.latestRound + 1 self.getAnswer[self.latestRound] = answer self.getTimestamp[self.latestRound] = block.timestamp self.getStartedAt[self.latestRound] = block.timestamp @external def updateRoundData( _roundId: uint256, answer: int256, timestamp: uint256, startedAt: uint256 ): self.latestRound = _roundId self.latestAnswer = answer self.latestTimestamp = timestamp self.getAnswer[self.latestRound] = answer self.getTimestamp[self.latestRound] = timestamp self.getStartedAt[self.latestRound] = startedAt @external @view def getRoundData(roundId: uint256) -> (uint256, int256, uint256, uint256, uint256): return ( roundId, self.getAnswer[roundId], self.getStartedAt[roundId], self.getTimestamp[roundId], roundId, ) @external @view def latestRoundData() -> (uint256, int256, uint256, uint256, uint256): return ( self.latestRound, self.getAnswer[self.latestRound], self.getStartedAt[self.latestRound], self.getTimestamp[self.latestRound], self.latestRound, ) ``` **Terminal Command to run the script** ```bash mox run deploy ``` **Code block for `buy_me_a_coffee.vy`** ```python # Storage funders: public(DynArray[address, 1000]) funder_to_amount_funded: public(HashMap[address, uint256]) # With constants: 262,853 @deploy def __init__(price_feed: address): PRICE_FEED = AggregatorV3Interface(price_feed) OWNER = msg.sender @external @payable def fund(): self._fund() @internal @payable def _fund(): """ Allows users to send $ to this contract Have a minimum $ amount to send How do we convert the ETH amount to dollars amount? ... """ usd_value_of_eth: uint256 = get_price_module.get_eth_to_usd_rate(PRICE_FEED, msg.value) assert usd_value_of_eth >= MINIMUM_USD, "You must spend more ETH!" self.funders.append(msg.sender) self.funder_to_amount_funded[msg.sender] += msg.value @external def withdraw(): """Take the money out of the contract, that people sent via the fund function. How do we make sure only we can pull the money out? ... """ assert msg.sender == OWNER, "Not the contract owner!" raw_call(OWNER, b"", value=self.balance) @external @view def get_eth_to_usd_rate(eth_amount: uint256) -> uint256: return get_price_module.get_eth_to_usd_rate(PRICE_FEED, eth_amount) @external @payable def default(): self._fund() ``` **Code Block for `get_price_module.vy`:** ```python from interfaces import AggregatorV3Interface PRECISION: constant(uint256) = 1 * (10 ** 18) @internal @view def _get_eth_to_usd_rate(price_feed: AggregatorV3Interface, eth_amount: uint256) -> uint256: """Chris sent us 0.01 ETH for us to buy a coffee Is that more or less than $5? ... """ price: int256 = staticcall(price_feed.latestAnswer()) eth_price_in_usd: uint256 = convert(price, uint256) * (10 ** 10) // (10 ** 18) eth_amount_in_usd: uint256 = (eth_price * eth_amount) // PRECISION return eth_amount_in_usd # 18 '0's, 18 decimal places ```