Hardhat is one of the most widely used development environments for building Ethereum-based applications. It provides a comprehensive suite of tools for compiling Solidity contracts, running tests, deploying to networks, and debugging transactions. For security researchers and auditors, understanding Hardhat is essential because many protocols use it as their primary development framework.

Core Features

Hardhat provides several features that make smart contract development more efficient and secure. The built-in local Ethereum network, Hardhat Network, allows developers to deploy contracts, run tests, and debug code in an isolated environment. This local network includes features like console.log support in Solidity, detailed stack traces, and the ability to fork mainnet state for realistic testing scenarios.

The framework uses a task-based architecture where common operations like compilation and testing are implemented as tasks that can be extended or overridden. This flexibility allows teams to customize their development workflow while maintaining compatibility with the broader ecosystem.

Hardhat vs Foundry

While Hardhat dominated the Ethereum development landscape for years, Foundry has emerged as a powerful alternative, particularly for security-focused work. The two frameworks represent different philosophies in smart contract development.

Hardhat tests are written in JavaScript or TypeScript, making them accessible to web developers transitioning to blockchain. The framework integrates well with the npm ecosystem and supports plugins for additional functionality. However, JavaScript-based tests can be slower and may not catch certain edge cases that Solidity-native tests would.

Foundry tests are written in Solidity itself, allowing for faster execution and more precise control over the EVM. Security researchers often prefer Foundry for fuzzing campaigns because its native Solidity tests can explore edge cases more efficiently. Many audit teams, including Zealynx, adapt Hardhat projects to Foundry for more rigorous testing.

Security Testing with Hardhat

For security audits, Hardhat provides several useful capabilities. The mainnet forking feature allows auditors to test contracts against real protocol state, catching integration issues that wouldn't appear in isolated testing. This is particularly valuable when auditing protocols that interact with existing DeFi infrastructure.

Hardhat also integrates with static analysis tools like Slither, enabling automated vulnerability detection as part of the development workflow. The framework's plugin architecture supports security-focused extensions for gas optimization analysis, storage layout inspection, and coverage reporting.

Working with Hardhat Projects

When auditing a project built with Hardhat, security researchers typically examine several key areas. The hardhat.config.js file defines network configurations, compiler settings, and plugin integrations. Understanding these settings helps identify potential issues like outdated compiler versions or missing optimizer configurations.

The test suite structure reveals how thoroughly the development team has tested their contracts. Sparse or superficial tests often correlate with undiscovered vulnerabilities. Auditors look for comprehensive unit tests, integration tests, and ideally fuzz tests that exercise edge cases.

Contract deployment scripts show how the protocol will be initialized in production. Misconfigured deployments, incorrect constructor arguments, or missing initialization calls can create critical vulnerabilities even in otherwise secure contracts.

Migration Considerations

Many security teams convert Hardhat projects to Foundry for auditing purposes. This migration involves translating JavaScript tests to Solidity and adapting the project structure. While this requires upfront effort, the resulting Foundry setup often enables more thorough invariant testing and fuzzing campaigns.

For protocols maintaining long-term codebases, supporting both frameworks provides flexibility. Hardhat remains excellent for deployment scripts and integration with web frontends, while Foundry excels at security testing and formal verification workflows.

Understanding both frameworks allows auditors to work effectively regardless of a project's chosen tooling, ensuring comprehensive security analysis across the diverse Ethereum ecosystem.