hardhat

Hardhat 3 supports two test layers: Solidity tests (.t.sol files) for unit tests running directly in the EVM, and TypeScript tests (test/*.ts) for off-chain orchestration. Run all tests with hardhat test, or scope to one layer with hardhat test solidity, nodejs, or mocha.

Use Solidity tests for unit tests on individual contracts since they compile-check against the real ABI and support cheatcodes and fuzzing. Use TypeScript tests only when you need multi-contract orchestration, shared fixtures, or external assertions about gas and balances.

Import Test from forge-std/Test.sol in your Solidity test contract to access the vm object. Common cheatcodes include vm.prank for msg.sender, vm.deal for balances, vm.warp for timestamps, and vm.expectRevert for revert assertions.

networkHelpers is a typed API exposed by network.create() for EVM state manipulation, covering time control, block mining, account impersonation, balance setting, loadFixture for cached deployments, and manual snapshots. It replaces raw JSON-RPC helper calls.

Generated contract types come from the compiled ABI, so you must compile before typechecking. Run npx hardhat build && npx tsc --noEmit so the compiler catches wrong argument types and invalid options like value on non-payable functions.

Yes, Solidity test functions with parameters (like testFuzz_Inc(uint8 x)) are automatically run with many random inputs. This works in any contract inheriting forge-std Test that contains at least one function whose name starts with test.