Unit testing

Unit test your integration with mock Hyperlane contracts
You can use the MockMailbox contract to unit test your integration with the Hyperlane messaging API.
You simply need to deploy MockMailbox contracts in your test environment, and configure your application to send and receive messages using these contracts.
The MockMailbox contract reflects the asynchronous nature of interchain messaging. In order to deliver a dispatched message to its recipient, you must call MockMailbox.processNextPendingMessage(), as shown in the examples below.
Using Foundry
Using Hardhat
// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;
import "forge-std/Test.sol";
import {MockMailbox} from "../src/mocks/MockMailbox.sol";
import {TestRecipient} from "../src/TestRecipient.sol";
contract MailboxTest is Test {
uint32 constant originDomain = 1000;
uint32 constant destinationDomain = 2000;
MockMailbox originMailbox;
MockMailbox destinationMailbox;
function setUp() public {
originMailbox = new MockMailbox(originDomain);
destinationMailbox = new MockMailbox(destinationDomain);
originMailbox.addRemoteMailbox(destinationDomain, destinationMailbox);
destinationMailbox.addRemoteMailbox(originDomain, originMailbox);
function testExample() public {
TestRecipient recipient = new TestRecipient();
bytes memory data = "This is a test message";
originMailbox.dispatch(destinationDomain, addressToBytes32(address(recipient)), data);
assertEq(recipient.data(), data);
function addressToBytes32(address _addr) internal pure returns (bytes32) {
return bytes32(uint256(uint160(_addr)));
describe("Hyperlane", function() {
it("should be able to send a message", async function () {
const MockMailbox = await ethers.getContractFactory("MockMailbox")
const TestRecipient = await ethers.getContractFactory("TestRecipient")
const originDomain = 1000
const originMailbox = await MockMailbox.deploy(originDomain)
const destinationDomain = 2000
const destinationMailbox = await MockMailbox.deploy(destinationDomain)
await originMailbox.enrollRemoteMailbox(destinationDomain, destinationMailbox.address)
await destinationMailbox.enrollRemoteMailbox(originDomain, originMailbox.address)
const recipient = await TestRecipient.deploy()
const data = ethers.utils.toUtf8Bytes("This is a test message")
await originMailbox.dispatch(destinationDomain, addressToBytes32(recipient.address), data)
await destinationMailbox.processNextPendingMessage()
const dataReceived = await recipient.data()

MockMailbox source

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;
interface IMessageRecipient {
function handle(
uint32 _origin,
bytes32 _sender,
bytes calldata _message
) external;
contract MockMailbox {
// Domain of chain on which the contract is deployed
uint32 public immutable domain;
uint32 public immutable version = 0;
uint256 public outboundNonce = 0;
uint256 public inboundUnprocessedNonce = 0;
uint256 public inboundProcessedNonce = 0;
mapping(uint32 => MockMailbox) public remoteMailboxes;
mapping(uint256 => Message) public inboundMessages;
struct Message {
uint32 origin;
address sender;
address recipient;
bytes body;
constructor(uint32 _domain) {
domain = _domain;
function addRemoteMailbox(uint32 _domain, MockMailbox _mailbox) external {
remoteMailboxes[_domain] = _mailbox;
function dispatch(
uint32 _destinationDomain,
bytes32 _recipientAddress,
bytes calldata _messageBody
) external returns (bytes32) {
MockMailbox _destinationMailbox = remoteMailboxes[_destinationDomain];
address(_destinationMailbox) != address(0),
"Missing remote mailbox"
return bytes32(0);
function addInboundMessage(
uint32 _origin,
address _sender,
address _recipient,
bytes calldata _body
) external {
inboundMessages[inboundUnprocessedNonce] = Message(
function processNextInboundMessage() public {
Message memory _message = inboundMessages[inboundProcessedNonce];
function bytes32ToAddress(bytes32 _buf) internal pure returns (address) {
return address(uint160(uint256(_buf)));
function addressToBytes32(address _addr) internal pure returns (bytes32) {
return bytes32(uint256(uint160(_addr)));

TestRecipient source

// SPDX-License-Identifier: MIT OR Apache-2.0
pragma solidity >=0.8.0;
interface IMessageRecipient {
function handle(
uint32 _origin,
bytes32 _sender,
bytes calldata _message
) external;
contract TestRecipient is IMessageRecipient {
bytes32 public sender;
bytes public data;
function handle(
bytes32 _sender,
bytes calldata _data
) external override {
sender = _sender;
data = _data;