Foundry

Foundry is the standard Solidity development toolkit. It compiles, tests, deploys, and interacts with smart contracts — all from the command line, all in Solidity (no JavaScript test wrappers). Four binaries: forge (build/test/deploy), cast (chain interaction), anvil (local EVM node), chisel (Solidity REPL).

What You Probably Got Wrong

LLMs have stale training data. These are the most common mistakes.

• forge create for deployments → Use forge script with --broadcast. forge create is for quick one-offs only — scripts are reproducible, support multi-contract deployments, and generate broadcast artifacts for verification.
• cast send returns data → cast send submits a transaction and returns a tx receipt. Use cast call to read return values (simulates without sending). Mixing these up is the #1 cast mistake.
• Old test assertion syntax → Foundry uses assertEq, assertGt, assertLt, assertTrue, assertFalse. There is no assert(a == b) pattern — it compiles but gives zero debug info on failure.
• vm.prank persists → vm.prank applies to the NEXT call only. Use vm.startPrank/vm.stopPrank for multiple calls from the same address.
• Anvil is just Ganache → Anvil supports mainnet forking at specific blocks (--fork-url + --fork-block-number), auto-impersonation, tracing, and mining modes. It's a full-featured local node.
• forge test -vvvv is overkill → Use -vv for logs/events, -vvv for execution traces on failures, -vvvv for full traces including setup. Start with -vv.
• --rpc-url with raw URLs → Use foundry.toml [rpc_endpoints] section or --rpc-url $ENV_VAR. Never paste RPC URLs directly in commands.
• Missing --via-ir for large contracts → If you hit "stack too deep", add via_ir = true in foundry.toml under [profile.default]. This enables the IR-based compilation pipeline.

Quick Start