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recon-extension

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Extension to Scaffold, Run and Debug Invariant Tests with Echidna, Medusa, Halmos and Foundry. Always published under Recon-Fuzz. Recommend building from source.

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# Recon - Smart Contract Fuzzing Extension

Scaffold and run Invariant Tests with Medusa, Echidna and Halmos, automatically debug broken properties with Foundry

<a href="#features">Features</a> •
 <a href="#installation">Installation</a> •
 <a href="#getting-started">Getting Started</a> •
 <a href="#usage">Usage</a> •
 <a href="#configuration">Configuration</a> •
 <a href="#troubleshooting">Troubleshooting</a> •
 <a href="#license">License</a>

---

## Features

The Recon extension is a VS Code extension that streamlines smart contract testing by providing:

- **One-click setup**: Automatically install and configure [Chimera](https://github.com/Recon-Fuzz/chimera) templates
- **Integrated fuzzing**: Run [Echidna](https://github.com/crytic/echidna), [Medusa](https://github.com/crytic/medusa) and [Halmos](https://github.com/a16z/halmos) directly from VS Code
- **Contract explorer**: Browse and select target contracts and functions
- **Fuzzer integration**: Quick access to fuzzing tools directly through the extension
- **Coverage visualization**: View and analyze code coverage from fuzzers
- **Test generation**: Generate Foundry unit tests from call sequences that break properties found by the fuzzer
- **Log to Foundry Repro converter**: Convert Echidna and Medusa logs to Foundry test reproductions with customizable VM options
- **Link Libraries (Experimental)**: Automatically detect and configure library dependencies for Echidna and Medusa
- **Mock/TargetFunctions generation**: Easily create mock contracts and target functions for testing
- **CodeLens integration**: Run tests and modify function behaviors directly in the editor

## Installation

### Prerequisites

- Visual Studio Code 1.88.0 or higher
- Foundry toolchain (forge, cast, anvil)
- Echidna (optional)
- Medusa (optional)
- Halmos (optional)

### Install from VS Code Marketplace

Official Link: https://marketplace.visualstudio.com/items?itemName=Recon-Fuzz.recon

1. Open VS Code
2. Go to Extensions (Ctrl+Shift+X)
3. Search for "Recon"
4. Click "Install"

### Manual Installation

1. Download the `.vsix` file from the [latest release](https://github.com/Recon-Fuzz/recon-extension/releases/latest)
2. In VS Code, go to Extensions
3. Click the "..." menu and select "Install from VSIX..."
4. Select the downloaded file

## Getting Started

1. Open a Foundry project in VS Code
2. Click on the Recon icon in the activity bar
3. In the Cockpit view, click "Scaffold" to set up a project using the [create-chimera-app](https://github.com/Recon-Fuzz/create-chimera-app/tree/main) template
4. Select target contracts and functions in the Contracts view
5. Run Echidna or Medusa from the status bar or Cockpit view

## Usage

For a comprehensive overview of how to use the extension for your fuzzing workflows see the [Recon Book](https://book.getrecon.xyz/free_recon_tools/recon_extension.html).

### Scaffolding a Project

The "Scaffold" button in the Recon Cockpit view will:

- Install Chimera as a Foundry submodule dependency
- Update `remappings.txt` with the necessary dependency remappings
- Create template files in the test/recon directory
- Configure your project for fuzzing

### Selecting Target Contracts and Functions

In the Contracts view you can:

1. Enable the contracts you want to test
2. For each contract, select the functions to include in the generated [`TargetFunctions`](https://book.getrecon.xyz/tutorial/chimera_framework.html#targetfunctions) contract
3. Configure function properties:
   - Actor: Regular user or admin
   - Mode: Normal execution, expected failure, or catch exceptions

### Running Fuzzers

- Use the status bar buttons for quick access to Echidna and Medusa
- Set the default fuzzer and configuration in the Cockpit view
- View live fuzzing progress in the output panel

### Viewing Coverage

After running a fuzzer with coverage enabled:

1. Go to the Coverage Reports view
2. Select a coverage report to view
3. Click the external icon to open the report in a browser view
4. Use the "Clean up Coverage Report" command for better readability

### Generating Mocks

Right-click on a contract's JSON artifact (located in the `out/` directory by default) or Solidity file and select "Generate Solidity Mock" to create a mock implementation of the contract.

### Converting Logs to Foundry Tests

The Log to Foundry converter helps you create reproducible Foundry tests from fuzzer outputs:

1. In the Recon Cockpit view, click "Tools" and select "Log to Foundry"
2. Select your fuzzer (Echidna or Medusa)
3. Paste the fuzzer log output into the text area
4. Click "Convert" to process the log
5. For each broken property found:
   - Toggle VM options (vm.prank, vm.roll, vm.warp) independently
   - View the generated Foundry test code with syntax highlighting
   - Copy individual properties or all properties at once
   - View the original trace if needed

## Configuration

Recon can be configured through VS Code settings:

### General Settings

- `recon.defaultFuzzer`: Choose between Echidna and Medusa
- `recon.showAllFiles`: Show or hide test and library files in the Contracts view
- `recon.foundryConfigPath`: Path to foundry.toml (relative to workspace root)

### Echidna Settings

- `recon.echidna.mode`: Configure [testing mode](https://secure-contracts.com/program-analysis/echidna/configuration.html#testmode) (assertion, property, etc.)
- `recon.echidna.testLimit`: Maximum number of test cases to run
- `recon.echidna.workers`: Number of parallel workers

### Medusa Settings

- `recon.medusa.testLimit`: Maximum number of test cases to run
- `recon.medusa.workers`: Number of parallel workers

### Forge Settings

- `recon.forge.buildArgs`: Additional arguments for forge build
- `recon.forge.testVerbosity`: Verbosity level for forge test output

## Troubleshooting

### Common Issues

- **Fuzzer not found**: Ensure Echidna/Medusa are installed and in your PATH
- **Compilation errors**: Run `forge build` manually to identify issues
- **No contracts showing**: Check if `out/` directory exists with compiled contracts
- Halmos log parser may have a few bugs
- The Vyper/foundry compiler integration doesn't have paths, so you have to fix them

## License

https://www.gnu.org/licenses/old-licenses/gpl-2.0.txt

recon-extension

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