VM

w3vm.VM is a high-level EVM environment with a simple but powerful API to simulate EVM execution, test Smart Contracts, or trace transactions. It supports Mainnet state forking via RPC and state caching for faster testing.

Example: Simulate an Uniswap v3 swap (Playground)

// 1. Create a VM that forks the Mainnet state from the latest block,
// disables the base fee, and has a fake WETH balance and approval for the router
vm, err := w3vm.New(
    w3vm.WithFork(client, nil),
    w3vm.WithNoBaseFee(),
    w3vm.WithState(w3types.State{
        addrWETH: {Storage: w3types.Storage{
            w3vm.WETHBalanceSlot(addrEOA):               common.BigToHash(w3.I("1 ether")),
            w3vm.WETHAllowanceSlot(addrEOA, addrRouter): common.BigToHash(w3.I("1 ether")),
        }},
    }),
)
if err != nil {
    // handle error
}
 
// 2. Simulate a Uniswap v3 swap
receipt, err := vm.Apply(&w3types.Message{
    From: addrEOA,
    To:   &addrRouter,
    Func: funcExactInput,
    Args: []any{&ExactInputParams{
        Path:             encodePath(addrWETH, 500, addrUNI),
        Recipient:        addrEOA,
        Deadline:         big.NewInt(time.Now().Unix()),
        AmountIn:         w3.I("1 ether"),
        AmountOutMinimum: w3.Big0,
    }},
})
if err != nil {
    // handle error
}
 
// 3. Decode output amount
var amountOut *big.Int
if err := receipt.DecodeReturns(&amountOut); err != nil {
    // handle error
}
ExtensionTracing