cast와 anvil

Beyond forge, Foundry ships cast and anvil. cast is a Swiss-army knife for interacting with chains and contracts from the terminal. anvil is a fast local Ethereum node for development.

Together they let you deploy, call, and inspect contracts without writing any application code.

Running anvil spins up a local chain at http://127.0.0.1:8545. It prints ten pre-funded accounts with their private keys, ready for testing.

By default it mines a block for every transaction instantly, so there is no waiting.

Anvil is highly configurable:

• --fork-url — fork a live network's state
• --block-time — mine on a fixed interval instead of per-transaction
• --accounts / --balance — control test accounts
• --chain-id — set the chain id

cast queries chain state directly. Common read commands:

• cast block-number — current block
• cast balance <addr> — ETH balance
• cast nonce <addr> — account nonce

cast call performs a read-only call to a contract function, returning the result without sending a transaction or spending gas.

cast send signs and broadcasts a state-changing transaction. You supply the contract address, the function signature, arguments, and a private key.

Cast handles ABI and data conversions:

• cast abi-encode / cast calldata — build calldata
• cast 4byte — look up a function selector
• cast --to-dec / --to-hex — number base conversion
• cast keccak — hash a value

After sending, inspect results:

• cast tx <hash> — transaction details
• cast receipt <hash> — receipt including gasUsed and logs
• cast run <hash> — replay with a full trace

cast run is invaluable for debugging why a transaction reverted.

Anvil exposes special RPC methods for testing, mirroring Foundry cheatcodes:

• anvil_setBalance — set any account's balance
• anvil_impersonateAccount — send as any address
• anvil_mine — mine blocks on demand
• evm_increaseTime — advance the clock

Call them through cast rpc.

A typical local loop:

• Start anvil in one terminal
• Deploy with forge script or forge create against it
• Use cast send and cast call to exercise the contract
• Debug failures with cast run

All without leaving the command line.

Combining anvil --fork-url with cast lets you experiment against a snapshot of mainnet locally: impersonate a whale, call a live protocol, and see real behavior without spending real funds.

This is the safest way to prototype interactions with deployed contracts.

You learned the cast and anvil tools:

• anvil runs a fast local node with pre-funded accounts and forking
• cast call reads state; cast send writes it
• Cast encodes/decodes calldata, hashes, and inspects receipts and traces
• cast run replays transactions for debugging
• Anvil RPC cheats manipulate balances, time, and mining

This completes the Foundry Toolkit course.