Popular Libraries for Development, Testing & Fuzzing

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Common Libraries & Tooling

Ethers and Viem serve similar purposes, but Viem is optimized for frontend apps. Wagmi builds on Viem. Web3.js is no longer recommended for new projects.

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Testing Frameworks

Note Smart contract quality and security depend on a comprehensive testing strategy including but not limited to:

• Unit Tests: Verify individual functions and components
• Property-Based Fuzzing: Test invariants with random inputs
• Code Coverage: Ensure all code paths are tested
• Static Analysis: Detect common vulnerabilities and anti-patterns

The tools and frameworks below provide a foundation for each of these testing layers.

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Foundry — Solidity-Native

• Tests written directly in Solidity.
• Very fast runner (forge test) and rich cheatcodes for state manipulation.
• Built-in, configurable fuzzing (forge test --fuzz-runs=N).
• Includes tools like forge script, forge coverage, and forge snapshot.

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Hardhat — JavaScript / TypeScript

• Mocha + Chai test runner for JS/TS-based tests.
• Flexible task system (hardhat.config.js), plugin support, and network forking.
• Integrates with Ethers.js and Solidity tooling for deployments, gas tracking, and test orchestration.

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v0.5.0 Compatibility Testing Framework

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EVM Tools Compatibility Testing

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Running Compatibility Tests

# Run JSON-RPC compatibility tests
cd /path/to/cosmos-evm
make test-rpc-compat  # Makefile:373

# Test specific tool
./scripts/tests_compatibility_foundry.sh
./scripts/tests_compatibility_hardhat.sh
./scripts/tests_compatibility_viem.sh
./scripts/tests_compatibility_web3js.sh
./scripts/tests_compatibility_foundry_uniswap_v3.sh

tests/evm-tools-compatibility/
├── foundry/          # Foundry compatibility tests
├── hardhat/          # Hardhat + Ethers.js tests
├── viem/             # Viem TypeScript tests
├── web3.js/          # Web3.js legacy tests
└── foundry-uniswap-v3/ # Complex DeFi protocol tests

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JSON-RPC Compatibility Testing

# Start comparison testing environment
cd tests/jsonrpc

# Build required Docker images
make localnet-build-env

# Start both evmd and geth for comparison
./scripts/start-networks.sh

# Run compatibility test suite
cd simulator && go build . && ./simulator

# Stop testing environment
./scripts/stop-networks.sh

• Transaction Processing: Compare transaction execution results
• Block Queries: Validate block structure and data
• Account Queries: Verify balance and nonce handling
• Event Logs: Ensure log filtering and retrieval accuracy
• Gas Estimation: Compare gas estimation algorithms

// tests/jsonrpc/simulator/config/config.go:27-36
type Config struct {
    EvmdHttpEndpoint string // Default: "http://localhost:8545"
    EvmdWsEndpoint   string // Default: "ws://localhost:8546"
    GethHttpEndpoint string // Default: "http://localhost:8547"
    GethWsEndpoint   string // Default: "ws://localhost:8548"
    RichPrivKey      string
    Timeout          string
}

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Fuzz (Property-Based) Testing

// test/MyContract.t.sol  (Foundry)
function test_myFunction_fuzz(uint256 amount) public {
    vm.assume(amount > 0 && amount < 1e18);   // constrain input
    myContract.myFunction(amount);
    assertEq(myContract.someState(), expectedValue);
}

• balance never exceeds total supply
• no overflow or underflow under bounded inputs
• access control is consistently enforced

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Supplementary Tools

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Example — OpenZeppelin Test Helpers

const { time, expectRevert } = require('@openzeppelin/test-helpers');

// advance clock by one day
await time.increase(time.duration.days(1));

// expect revert with specific reason
await expectRevert(contract.someFunction(), "Ownable: caller is not the owner");