39. Testing with Brownie/Ape

Brownie and its successor Ape are Python frameworks that support both Solidity and Vyper projects, letting you write pytest-style tests, manage deployments, and fork mainnet state for integration tests.

def test_transfer(token, accounts):
    token.transfer(accounts[1], 100, {"from": accounts[0]})
    assert token.balanceOf(accounts[1]) == 100

Mainnet forking is especially valuable for Vyper DeFi contracts: you can test real interactions against deployed protocols (like an actual Uniswap pool) without spending real ETH.

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