smart-contract-testing

Smart Contract Testing

When to use this skill

Use when the user asks about:

• Writing tests for smart contracts
• Setting up a testing framework (Foundry or Hardhat)
• Fuzz testing or invariant testing strategies
• Fork testing against mainnet state
• Gas benchmarking and optimization verification
• Debugging failing contract tests

Testing Framework Selection

Foundry vs Hardhat

Feature	Foundry	Hardhat
Language	Solidity	JavaScript/TypeScript
Speed	Very fast (native)	Slower (JS runtime)
Fuzzing	Built-in	Requires plugins
Fork testing	Built-in	Built-in
Debugging	forge debug, traces	console.sol, traces
Ecosystem	Growing rapidly	Mature, large plugin ecosystem

Recommendation: Use Foundry for new projects. Use Hardhat when you need complex JS scripting or specific Hardhat plugins.

Testing with Foundry

1. Unit Test Structure

Follow this pattern for each test:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

import {Test} from "forge-std/Test.sol";
import {MyContract} from "../src/MyContract.sol";

contract MyContractTest is Test {
    MyContract internal target;
    address internal alice = makeAddr("alice");
    address internal bob = makeAddr("bob");

    function setUp() public {
        target = new MyContract();
        deal(alice, 100 ether);
    }

    function test_deposit_succeeds() public {
        vm.prank(alice);
        target.deposit{value: 1 ether}();
        assertEq(target.balanceOf(alice), 1 ether);
    }

    function test_deposit_revertsWhenZero() public {
        vm.prank(alice);
        vm.expectRevert(MyContract.ZeroAmount.selector);
        target.deposit{value: 0}();
    }
}

Naming conventions:

• test_functionName_scenario for expected-pass tests
• test_functionName_revertsWhen_condition for expected-revert tests
• testFuzz_functionName for fuzz tests

2. Fuzz Testing

Let Foundry generate random inputs to find edge cases: