title	description
Use Hardhat with Polkadot Hub	Learn how to create, compile, test, and deploy smart contracts on Polkadot Hub using Hardhat, a powerful development environment for blockchain developers.

Hardhat

- :octicons-code-16:{ .lg .middle } __Test and Deploy with Hardhat__

---

Master Solidity smart contract development with Hardhat. Learn testing, deployment, and network interaction in one comprehensive tutorial.

<br>
[:octicons-arrow-right-24: Get Started](/tutorials/smart-contracts/launch-your-first-project/test-and-deploy-with-hardhat){target=\_blank}

Overview

Hardhat is a robust development environment for Ethereum-compatible chains that makes smart contract development more efficient. This guide walks you through the essentials of using Hardhat to create, compile, test, and deploy smart contracts on Polkadot Hub.

Prerequisites

Before getting started, ensure you have:

Node.js{target=_blank} (v16.0.0 or later) and npm installed
Basic understanding of Solidity programming
Some WND test tokens to cover transaction fees (easily obtainable from the Polkadot faucet{target=_blank}). To learn how to get test tokens, check out the Test Tokens{target=_blank} section
MetaMask{target=_blank} installed and connected to Westend Hub{target=_blank}. For more detailed instructions on connecting your wallet, see the Connect Your Wallet{target=_blank} section

Setting Up Hardhat

Create a new directory for your project and navigate into it:
```
mkdir hardhat-example
cd hardhat-example
```
Initialize a new npm project:
```
npm init -y
```
Install Hardhat and the required plugins:
```
npm install --save-dev hardhat @nomicfoundation/hardhat-toolbox
```
To interact with Polkadot Hub, Hardhat requires the hardhat-resolc{target=_blank} plugin to compile contracts to PolkaVM bytecode and the hardhat-revive-node{target=_blank} plugin to spawn a local node compatible with PolkaVM.
```
npm install --save-dev hardhat-resolc hardhat-revive-node
```
Create a Hardhat project:
```
npx hardhat init
```
Select "Create a JavaScript project" when prompted and follow the instructions. After that, your project will be created with three main folders:
- contracts - where your Solidity smart contracts live
- test - contains your test files that validate contract functionality
- ignition - deployment modules for safely deploying your contracts to various networks

Update your Hardhat configuration file (hardhat.config.js) to include the plugins:

--8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:0:12'
--8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:15:16'
  // Additional configuration will be added later
--8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:66:66'

Compiling Your Contract

The hardhat-resolc plugin will compile your Solidity contracts for Solidity versions 0.8.0 and higher to be PolkaVM compatible. When compiling your contract using the hardhat-resolc plugin, there are two ways to configure your compilation process:

Remix compiler - uses the Remix online compiler backend for simplicity and ease of use
Binary compiler - uses the resolc binary directly for more control and configuration options

To compile your project, follow these instructions:

Modify your Hardhat configuration file to specify which compilation process you will be using:

=== "Remix Configuration"

 ```javascript title="hardhat.config.js" hl_lines="15-25"
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:0:12'
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:15:17'
   --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:19:29'
   --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:43:45'
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:65:66'
 ```

=== "Binary Configuration"

 ```javascript title="hardhat.config.js" hl_lines="15-26"
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:0:12'
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:15:17'
   --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:31:42'
   --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:43:45'
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:65:66'
 ```

For the binary configuration, replace INSERT_PATH_TO_RESOLC_COMPILER with the proper path to the binary. For more information about its installation, check the installation{target=_blank} section of the pallet-revive.

Compile the contract with Hardhat:
```
npx hardhat compile
```
After successful compilation, you'll see the artifacts generated in the artifacts-pvm directory:
```
ls artifacts-pvm/contracts/*.sol/
```
You should see JSON files containing the contract ABI and bytecode of the contracts you compiled.

Testing Your Contract

When testing your contract, be aware that @nomicfoundation/hardhat-toolbox/network-helpers{target=_blank} is not fully compatible with Polkadot Hub's available RPCs. Specifically, Hardhat-only helpers like time and loadFixture may not work due to missing RPC calls in the node. For more details, refer to the Compatibility{target=_blank} section in the hardhat-revive docs.

You should avoid using helpers like time and loadFixture when writing tests. For example, for the Lock.sol contract, you can replace the default test file under tests/Lock.js with the following logic:

--8<-- "code/develop/smart-contracts/dev-environments/hardhat/lock-test.js"

To run your test, execute the following command:

npx hardhat test

Deploying with a Local Node

Before deploying to a live network, you can deploy your contract to a local node using the hardhat-revive-node{target=_blank} plugin and Ignition modules:

!!! warning "Contract Size Limitation in Testing Environment"

When testing or deploying large contracts in Hardhat's local environment, you may encounter this error:

`Error: the initcode size of this transaction is too large`

This limitation is established by Hardhat based on Ethereum's default contract size limits. While Hardhat can disable this limitation, technical constraints currently prevent it from being applied to the PolkaVM test environment.

First, ensure you have compiled a Substrate node and the ETH RPC adapter from the Polkadot SDK. Checkout the compatible commit{target=_blank} from the SDK and build the node and the ETH-RPC from source:
```
git clone https://github.com/paritytech/polkadot-sdk.git
cd polkadot-sdk
git checkout {{ dependencies.repositories.polkadot_sdk_compatible_hardhat_node }}
```
Now, build the node and the ETH-RPC adapter. Note that this process might take a long time to complete:
```
# Build the substrate node
cargo build --release
# Build the eth-rpc adapter
cargo build -p pallet-revive-eth-rpc --bin eth-rpc --release
```

Update the Hardhat configuration file to add the local node as a target for local deployment:

=== "Remix Configuration"

 ```javascript title="hardhat.config.js" hl_lines="27-44"
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:0:12'
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:15:29'
   --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:43:59'
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:65:66'
 ```

=== "Binary Configuration"

 ```javascript title="hardhat.config.js" hl_lines="27-44"
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:0:12'
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:15:17'
   --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:31:42'
   --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:43:59'
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:65:66'
 ```

Ensure to replace INSERT_PATH_TO_SUBSTRATE_NODE and INSERT_PATH_TO_ETH_RPC_ADAPTER with the proper paths to the compiled binaries. Since you compiled these from source using Rust's Cargo build system, you can find them at:

Substrate node path - polkadot-sdk/target/release/substrate-node
ETH-RPC adapter path - polkadot-sdk/target/release/eth-rpc

For example, if you cloned the polkadot-sdk repository to your home directory, the paths might look like:

nodeBinaryPath: '/home/username/polkadot-sdk/target/release/substrate-node',
adapterBinaryPath: '/home/username/polkadot-sdk/target/release/eth-rpc',

Modify the Ignition modules, considering that the value of the pallet revive block.timestamp is returned in seconds. Check this PR{target=_blank} for more information. For example, for the default ignition/modules/Lock.js file, the needed modification should be:
```
- const JAN_1ST_2030 = 1893456000;
+ const JAN_1ST_2030 = 18934560000000;
```
???--- code "Modified ignition/modules/Lock.js file"
```
 ```js title="Lock.js"
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/lock-ignition.js'
 ```
```
Start a local node:
```
npx hardhat node-polkavm
```
This command will start a local PolkaVM node powered by the hardhat-revive-node plugin.
In a new terminal window, deploy the contract using Ignition:
```
npx hardhat ignition deploy ./ignition/modules/INSERT_IGNITION_MODULE_NAME.js --network localNode
```
Replace INSERT_IGNITION_MODULE_NAME with the proper name for your contract. You'll see deployment information, including the contract address.

Deploying to a Live Network

After testing your contract locally, you can deploy it to a live network. This guide will use Westend Hub as the target network. Here's how to configure and deploy:

Fund your deployment account with enough tokens to cover gas fees. In this case, the needed tokens are WND (on Westend). You can use the Polkadot faucet{target=_blank} to obtain testing tokens.
Export your private key and save it in a .env file:
```
PRIVATE_KEY="INSERT_PRIVATE_KEY"
```
Replace INSERT_PRIVATE_KEY with your actual private key. For further details on private key exportation, refer to the article How to export an account's private key{target=_blank}.

!!! warning Never reveal your private key. Be sure you add the .env file to your .gitignore file.
Install the dotenv{target=_blank} package to load the private key into your Hardhat configuration:
```
npm install dotenv
```

Update your config to load it:

--8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:0:16'
  // The rest remains the same...
--8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:66:66'

Update your Hardhat configuration file with network settings for the Polkadot network you want to target:

=== "Remix Configuration"

 ```javascript title="hardhat.config.js" hl_lines="44-48"
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:0:12'
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:15:29'
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:43:66'
 ```

=== "Binary Configuration"

 ```javascript title="hardhat.config.js" hl_lines="44-48"
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:0:12'
 --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:15:17'
   --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:31:42'
   --8<-- 'code/develop/smart-contracts/dev-environments/hardhat/hardhat.config.js:43:66'
 ```

Deploy your contract using Ignition:
```
npx hardhat ignition deploy ./ignition/modules/INSERT_IGNITION_MODULE_NAME.js --network westendAssetHub
```
Replace INSERT_IGNITION_MODULE_NAME with the proper name for your contract. You'll see deployment information, including the contract address.

Interacting with Your Contract

Once deployed, you can create a script to interact with your contract. To do so, create a file called scripts/interact.js and add some logic to interact with the contract.

For example, for the default Lock.sol contract, you can use the following file that connects to the contract at its address and retrieves the unlockTime, which represents when funds can be withdrawn. The script converts this timestamp into a readable date and logs it. It then checks the contract's balance and displays it. Finally, it attempts to call the withdrawal function on the contract, but it catches and logs the error message if the withdrawal is not yet allowed (e.g., before unlockTime).

--8<-- 'code/develop/smart-contracts/dev-environments/hardhat/interact.js'

Run your interaction script:

npx hardhat run scripts/interact.js --network westendAssetHub

Where to Go Next

Hardhat provides a powerful environment for developing, testing, and deploying smart contracts on Polkadot Hub. Its plugin architecture allows seamless integration with PolkaVM through the hardhat-resolc and hardhat-revive-node plugins.

Explore more about smart contracts through these resources:

Guide Smart Contracts on Polkadot

Dive into advanced smart contract concepts.

:octicons-arrow-right-24: Get Started
External Hardhat Documentation

Learn more about Hardhat's advanced features and best practices.

:octicons-arrow-right-24: Get Started{target=_blank}
External OpenZeppelin Contracts

Test your skills by deploying contracts with prebuilt templates.

:octicons-arrow-right-24: Get Started{target=_blank}

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hardhat.md

hardhat.md

Hardhat

Overview

Prerequisites

Setting Up Hardhat

Compiling Your Contract

Testing Your Contract

Deploying with a Local Node

Deploying to a Live Network

Interacting with Your Contract

Where to Go Next

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hardhat.md

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hardhat.md

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Hardhat

Overview

Prerequisites

Setting Up Hardhat

Compiling Your Contract

Testing Your Contract

Deploying with a Local Node

Deploying to a Live Network

Interacting with Your Contract

Where to Go Next