# Chainlink Local: Develop and Test Chainlink Services Chainlink Local is a development package that allows you to run Chainlink services directly in your local environment. This tool enables developers to explore Chainlink services before deploying to testnets or mainnet. ## What is Chainlink Local? Chainlink Local is an installable package that integrates with popular development environments like [Foundry](https://getfoundry.sh/), [Hardhat](https://hardhat.org/), and [Remix](https://remix.ethereum.org/). It allows you to run Chainlink services locally for rapid development and testing. For example, you can use Chainlink Local to execute CCIP cross-chain messages on a local node. ## Key Features - **Local Simulation**: Test Chainlink services on local blockchain nodes. - **Forked Networks**: Work with deployed Chainlink contracts using forked networks for realistic testing. - **Seamless Integration**: Compatible with [Foundry](https://getfoundry.sh/), [Hardhat](https://hardhat.org/), and [Remix](https://remix.ethereum.org/) development environments. - **Testnet-Ready Code**: Contracts tested locally can be deployed to testnets without modifications. ## Development Modes Chainlink Local supports two primary testing approaches: ### 1. Local Testing Without Forking In this mode, you work with mock Chainlink contracts on a locally running node (such as HardHat, Anvil, or Remix VM): - Deploy mock Chainlink smart contracts to a blank EVM state. - Deploy your smart contracts and test them with these local implementations. - Ideal for initial development and basic functionality testing. **Note**: We will use this in the subsequent lesson. ### 2. Local Testing With Forking This more advanced mode uses forked blockchains: - Fork one or more live blockchains to create a realistic testing environment. - Interact with deployed Chainlink contracts through the provided interfaces. - Switch between different forked chains (e.g., source and destination chains for CCIP testing). - Not supported in [Remix](https://remix.ethereum.org/), only on [Hardhat](https://hardhat.org/) and [Foundry](https://getfoundry.sh/). ## Developer benefits Chainlink Local enables developers to: - Execute CCIP token transfers and arbitrary messages on local nodes. - Test cross-chain functionality between multiple local forks. - Rapidly test Chainlink-dependent smart contracts. - Verify contract behavior in a controlled environment before testnet deployment.