# Truffle

Set up a Truffle Ethermint local development environment.

# Pre-requisite Readings

Truffle is a development framework for deploying and managing Solidity smart contracts. In this guide, we will learn how to deploy a contract to a running Ethermint network.

# Install dependencies

First, install the latest Truffle version on your machine globally.

Copy yarn install truffle -g

You will also need to install Ethermint. Check this document for the full instructions.

# Create Truffle Project

In this step we will create a simple counter contract. Feel free to skip this step if you already have your own compiled contract.

Create a new directory to host the contracts and initialize it

Copy mkdir ethermint-truffle cd ethermint-truffle

Initialize the Truffle suite with:

Copy truffle init

Create contracts/Counter.sol containing the following contract:

Copy pragma solidity ^0.5.11; contract Counter { uint256 counter = 0; function add() public { counter++; } function subtract() public { counter--; } function getCounter() public view returns (uint256) { return counter; } }

Compile the contract using the compile command:

Copy truffle compile

Create test/counter_test.js containing the following tests in Javascript using Mocha:

Copy const Counter = artifacts.require("Counter") contract('Counter', accounts => { const from = accounts[0] let counter before(async() => { counter = await Counter.new() }) it('should add', async() => { await counter.add() let count = await counter.getCounter() assert(count == 1, `count was ${count}`) }) })

# Truffle configuration

Open truffle-config.js and uncomment the development section in networks:

Copy development: { host: "", // Localhost (default: none) port: 8545, // Standard Ethereum port (default: none) network_id: "*", // Any network (default: none) },

This will allow your contract to connect to your Ethermint local node.

# Start Node and REST server

Start your local node using the following command on the Terminal

Copy # on the ~/ethermint/ directory init.sh

For further information on how to run a node, please refer to this quickstart document.

In another Terminal wintdow/tab, start the REST and JSON-RPC server:

Copy ethermintcli rest-server --laddr "tcp://localhost:8545" --unlock-key mykey--chain-id 8 --trace

# Deploy contract

Back in the Truffle terminal, migrate the contract using

Copy truffle migrate --network development

You should see incoming deployment logs in the Ethermint daemon Terminal tab for each transaction (one to deploy Migrations.sol and the oether to deploy Counter.sol).

Copy I[2020-07-15|17:35:59.934] Added good transaction module=mempool tx=22245B935689918D332F58E82690F02073F0453D54D5944B6D64AAF1F21974E2 res="&{CheckTx:log:\"[]\" gas_wanted:6721975 }" height=3 total=1 I[2020-07-15|17:36:02.065] Executed block module=state height=4 validTxs=1 invalidTxs=0 I[2020-07-15|17:36:02.068] Committed state module=state height=4 txs=1 appHash=76BA85365F10A59FE24ADCA87544191C2D72B9FB5630466C5B71E878F9C0A111 I[2020-07-15|17:36:02.981] Added good transaction module=mempool tx=84516B4588CBB21E6D562A6A295F1F8876076A0CFF2EF1B0EC670AD8D8BB5425 res="&{CheckTx:log:\"[]\" gas_wanted:6721975 }" height=4 total=1

# Run Truffle tests

Now, you can run the Truffle tests using the Ethermint node using the test command:

Copy truffle test --network development Using network 'development'. Compiling your contracts... =========================== > Everything is up to date, there is nothing to compile. Contract: Counter ✓ should add (5036ms) 1 passing (10s)

# Next

Learn how to connect Ethermint to Metamask