Forking Mainnet Example

import { createTevmNode } from 'tevm'
import { http } from 'viem'
 
const node = createTevmNode({
  fork: {
    transport: http('https://mainnet.infura.io/v3/<yourkey>'),
    blockTag: 17_000_000n,
  },
  loggingLevel: 'debug',
})
 
await node.ready()
 
// Now any calls to an unknown account or contract
// will fetch the data from mainnet, but store the result locally for caching.

// Impersonate a whale account
node.setImpersonatedAccount('0x28C6c06298d514Db089934071355E5743bf21d60') // Binance 14
 
// Now you can run transactions "as" that address, no signature needed
const tx = createImpersonatedTx({
  to: '0x1234...',
  value: 1000000000000000000n, // 1 ETH
})
 
const vm = await node.getVm()
await vm.runTx({ tx })

// Example: Interacting with USDC on mainnet
const USDC_ADDRESS = '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48'
 
// Get the contract state from mainnet
const usdcContract = new Contract(USDC_ADDRESS, USDC_ABI)
const balance = await usdcContract.read.balanceOf(['0x1234...'])
 
// Modify state locally
await usdcContract.write.transfer(['0x5678...', 1000000]) // 1 USDC
 
// Changes only affect your local fork
const newBalance = await usdcContract.read.balanceOf(['0x1234...'])

const node = createTevmNode({
  fork: {
    transport: http('https://mainnet.infura.io/v3/<yourkey>'),
    blockTag: 15_000_000n, // Fork from a specific block
  },
})
 
// Test historical state
const historicalBalance = await getBalance(address)

// Fork from different networks
const optimismNode = createTevmNode({
  fork: {
    transport: http('https://mainnet.optimism.io'),
  },
})
 
const arbitrumNode = createTevmNode({
  fork: {
    transport: http('https://arb1.arbitrum.io/rpc'),
  },
})