Advanced Foundry Testing Guide 🔨

A comprehensive guide to advanced testing patterns in Foundry for Ethereum smart contract development. This repository contains all the code examples and patterns discussed in my Medium blog series.

📝 Blog Post

I've written an in-depth article about advanced Foundry testing patterns. Read it on Medium:

Advanced Foundry Testing Patterns: A Complete Guide

This repository serves as the companion code for the blog post, providing working examples of all the patterns and techniques discussed.

🎯 What's Inside

This guide covers advanced testing patterns that go beyond basic unit tests:

Core Testing Patterns

• ✅ State tree testing
• ✅ Time-based testing patterns
• ✅ Access control testing
• ✅ Event testing with vm.expectEmit
• ✅ Snapshot and rollback patterns

Advanced Techniques

• 🔍 Fuzz testing with bounds and assumptions
• 🔄 Invariant testing with handlers
• 🍴 Fork testing with mainnet state
• 🔐 Security pattern testing (reentrancy, access control)
• 📊 Gas optimization testing
• 🔄 Differential testing
• 🎭 Mock and stub patterns

Real-World Scenarios

• 💸 DeFi protocol integration testing
• 🌉 Cross-chain bridge testing
• ⬆️ Proxy and upgradeability testing
• 🚨 Attack vector testing
• 💰 Multi-user stateful fuzzing

📚 Documentation Files

Main Guides

• foundry-advanced-guide.md - Core testing patterns and fundamentals
• foundry-real-world-examples.md - Production scenarios and security testing

Code Examples

All examples are fully functional and can be run with Foundry.

🚀 Getting Started

Prerequisites

Make sure you have Foundry installed:

curl -L https://foundry.paradigm.xyz | bash
foundryup

Installation

1. Clone the repository:

git clone https://github.com/jmakwana0x1/foundry-advanced-testing.git
cd foundry-advanced-testing

2. Install dependencies:

forge install

3. Run the tests:

forge test

Running Specific Examples

# Run all tests
forge test

# Run tests with gas reporting
forge test --gas-report

# Run specific test file
forge test --match-path test/ReentrancyTest.t.sol

# Run with verbosity for detailed output
forge test -vvvv

# Run fuzz tests only
forge test --match-test testFuzz

# Run invariant tests
forge test --match-test invariant

# Generate coverage report
forge coverage

# Create gas snapshot
forge snapshot

📖 Guide Structure

1. Basic Testing Patterns

Learn the fundamentals of writing effective Foundry tests:

• Setting up test environments
• Using cheat codes (vm.prank, vm.warp, vm.roll)
• Assertions and expectations
• Test organization

2. Fuzz Testing

Master property-based testing:

• Bounded fuzzing with bound()
• Using assumptions with vm.assume()
• Testing invariants across random inputs
• Structured fuzzing strategies

3. Invariant Testing

Build robust invariant test suites:

• Handler-based testing
• Ghost variables for tracking
• Multi-actor scenarios
• Stateful fuzzing patterns

4. Fork Testing

Test against real deployed contracts:

• Creating and managing forks
• Impersonating accounts
• Testing with live data
• Multi-chain testing

5. Security Testing

Identify vulnerabilities:

• Reentrancy attack patterns
• Access control bypass testing
• Flash loan manipulation
• Integer overflow/underflow
• Front-running scenarios

6. Gas Optimization

Optimize your contracts:

• Gas profiling techniques
• Comparative gas analysis
• Snapshot-based regression testing
• Identifying optimization opportunities

🔧 Project Structure

foundry-advanced-testing/
├── README.md
├── foundry-advanced-guide.md
├── foundry-real-world-examples.md
├── foundry.toml
├── src/
│   ├── examples/
│   │   ├── Token.sol
│   │   ├── Vault.sol
│   │   ├── LendingPool.sol
│   │   ├── AMM.sol
│   │   └── ...
│   └── security/
│       ├── VulnerableBank.sol
│       ├── ProtectedBank.sol
│       └── ...
└── test/
    ├── unit/
    │   ├── Token.t.sol
    │   └── Vault.t.sol
    ├── integration/
    │   ├── DeFiIntegration.t.sol
    │   └── MultiContract.t.sol
    ├── invariant/
    │   ├── BankInvariant.t.sol
    │   └── AMMInvariant.t.sol
    ├── fork/
    │   └── MainnetFork.t.sol
    └── security/
        ├── ReentrancyTest.t.sol
        └── AccessControlTest.t.sol

💡 Key Concepts

Cheat Codes Reference

Cheat Code	Purpose	Example
vm.prank(address)	Set msg.sender for next call	vm.prank(alice); token.transfer(bob, 100);
vm.startPrank(address)	Set msg.sender for all calls	vm.startPrank(alice);
vm.warp(timestamp)	Set block.timestamp	vm.warp(block.timestamp + 1 days);
vm.roll(number)	Set block.number	vm.roll(block.number + 100);
vm.deal(address, amount)	Set ETH balance	vm.deal(alice, 100 ether);
vm.expectRevert()	Expect next call to revert	vm.expectRevert("Error");
vm.expectEmit()	Expect event emission	vm.expectEmit(true, true, false, true);

Test Naming Conventions

test_Description()              // Basic test
testFail_Description()          // Expected to fail (deprecated, use expectRevert)
testRevert_Description()        // Expect revert with reason
testFuzz_Description(args)      // Fuzz test
invariant_Description()         // Invariant test

🎓 Learning Path

1. Start with the basics - Read foundry-advanced-guide.md sections 1-3
2. Try simple examples - Run the unit tests
3. Explore fuzzing - Understand property-based testing
4. Master invariants - Build handler-based test suites
5. Real-world scenarios - Study foundry-real-world-examples.md
6. Security focus - Learn attack vectors and defenses

🛠️ Advanced Configuration

foundry.toml

[profile.default]
src = "src"
out = "out"
libs = ["lib"]
solc_version = "0.8.24"

[profile.default.fuzz]
runs = 256
max_test_rejects = 65536

[profile.default.invariant]
runs = 256
depth = 15
fail_on_revert = false

[profile.ci]
fuzz = { runs = 5000 }
invariant = { runs = 1000 }

📊 Example Test Output

$ forge test --gas-report

Running 47 tests for test/Token.t.sol:TokenTest
[PASS] test_Mint() (gas: 45123)
[PASS] test_Transfer() (gas: 67234)
[PASS] testFuzz_TransferAmounts(uint256) (runs: 256, μ: 65432, ~: 65234)
[PASS] invariant_totalSupplyEqualsBalances() (runs: 256, calls: 3840, reverts: 156)

Test result: ok. 47 passed; 0 failed; finished in 2.34s

| Contract | Function      | Gas     |
|----------|---------------|---------|
| Token    | mint          | 45123   |
| Token    | transfer      | 67234   |
| Token    | approve       | 44567   |

🤝 Contributing

While this is primarily an educational repository for my blog post, I welcome:

• 🐛 Bug reports
• 💡 Suggestions for additional patterns
• 📝 Improvements to documentation
• ✨ Additional examples

Please open an issue or submit a pull request!

📬 Contact & Follow

• Medium: @YOUR_MEDIUM_USERNAME
• Twitter: @YOUR_TWITTER
• GitHub: @YOUR_GITHUB

If you found this guide helpful, please:

• ⭐ Star this repository
• 👏 Clap for the Medium article
• 🔄 Share with fellow developers

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• The Foundry team for creating an amazing development framework
• The Ethereum development community
• Everyone who contributed feedback and suggestions

📚 Additional Resources

• Foundry Book - Official Foundry documentation
• Foundry GitHub - Source code and issues
• Ethereum Smart Contract Best Practices
• Smart Contract Security

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Happy Testing! 🎉

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Made with ❤️ for the Ethereum developer community

_{Last updated: February 2026}