# Writing some Solidity unit tests with Truffle

**Published by:** [Frank 🐢](https://paragraph.com/@frankturtle/)
**Published on:** 2021-12-12
**URL:** https://paragraph.com/@frankturtle/writing-some-solidity-unit-tests-with-truffle

## Content

Writing some Solidity unit tests with Truffle You are unit testing, right 👀👀?! Table of contents TL;DR Unit what now? Tiny baby Solidity smart contract ✍ those Tests LETS RUN THOSE TESTS 🚀🚀 Recap Picture Credits TL;DR Write some damn tests so you have proof your code does what you think it does! Unit what now? I'm going to pretend you did not ask that question 😆. Unit testing is one of the best skills you should be practicing as you continue your growth as an engineer. But this entry isn't really going to get into the why. I'll save that one for later 😉 This isn't going to be too crazy, merely a little tiny baby introduction to unit testing your Solidity smart contract. Savvy? braden-collum-9HI8UJMSdZA-unsplash.jpg Tiny baby Solidity smart contract Let's start with a real basic smart contract. A typical ToDo list tends to be a good jumping off point with these things. pragma solidity ^0.8.0; contract TodoList { uint256 public taskCount = 0; struct Task { uint256 id; string content; bool completed; } mapping(uint256 => Task) public tasks; function createTask(string memory _content) public { taskCount++; tasks[taskCount] = Task(taskCount, _content, false); } } You can see the following: a taskCounter to keep track of all the Tasks needing completed ✅ a Task struct which will encapsulate the information needed inside each of the Tasks for us a simple mapping to, well, map the Tasks after writing the word Task so many times just now, I am suffering from Semantic Satiation -- I caught myself re-reading that bullet list several times because it was not making sense to me anymore 🤣 Super, let's move on to writing our sweet test!! GOOD JOB! johan-godinez-dDYRYivNzbI-unsplash.jpg ✍ those Tests The emoji is a bit of a lie, you are not actually going to handwrite your tests. Although, if you wanted to, you absolutely could! Actually, when I started out programming, I would handwrite all my Java code 🤷‍♀️🤷‍♀️ AAAAAAAAAAanyway ⏪ I guess we missed a few steps, let's backtrack slightly. ⏪ You're going to need to setup Truffle! Hit up your terminal, at the root of your project and type 👇 $ truffle init contracts already exists in this directory... ? Overwrite contracts? (y/N) Starting init... ================ ? Overwrite contracts? No > Copying project files to C:\Users\frank🐢\Documents\Solidity-Unit-Testing Init successful, sweet! Try our scaffold commands to get started: $ truffle create contract YourContractName # scaffold a contract $ truffle create test YourTestName # scaffold a test http://trufflesuite.com/docs Take note that you will need to hit N to avoid overwriting your amazingly cool ToDoList.sol contract we just wrote! SCHWEET, now we're back in business 🤙🤙 OK, so now your folder structure should look something like this ( note, it's not going to be exact b/c I had created a readme, .gitignore, npm project ): BeautyShot-67708.png Let's go ahead and create a new test file in our /test folder and name it ToDoList.test.js const TodoList = artifacts.require("./TodoList.sol"); contract("TodoList", accounts => { const creatorAddress = accounts[0]; const firstOwnerAddress = accounts[1]; const secondOwnerAddress = accounts[2]; const externalAddress = accounts[3]; const unprivilegedAddress = accounts[4] /* create named accounts for contract roles */ before(async () => { this.todoList = await TodoList.deployed(); }); it('should deploy successfully', async () => { assert.notEqual(creatorAddress, 0x0); assert.notEqual(creatorAddress, ''); assert.notEqual(creatorAddress, null); assert.notEqual(creatorAddress, undefined); }); it('should revert if ...', async () => { try { const result = this.todoList.publicOrExternalContractMethod(argument1, argument2, { from: externalAddress }); assert.fail(); } catch (error) { assert.notEqual(error.message, "assert.fail()", "Reason ..."); } }); it('should lists tasks', async () => { const taskCount = await this.todoList.taskCount(); const task = await this.todoList.tasks(taskCount); assert.equal(task.id.toNumber(), taskCount.toNumber()); assert.equal(task.completed, false); assert.equal(taskCount.toNumber(), 0); }); }); Save the file and ... LETS RUN THOSE TESTS 🚀🚀 Type in the command truffle test and you should see something similar to this: $ truffle test Using network 'test'. Compiling your contracts... =========================== > Compiling .\contracts\ToDoList.sol > Compilation warnings encountered: Warning: SPDX license identifier not provided in source file. Before publishing, consider adding a comment containing "SPDX-License-Identifier: <SPDX-License>" to each source file. Use "SPDX-License-Identifier: UNLICENSED" for non-open-source code. Please see https://spdx.org for more information. --> project:/contracts/ToDoList.sol > Artifacts written to C:\Users\frank🐢\AppData\Local\Temp\test--3584-6JQ8tVvSUA5L > Compiled successfully using: - solc: 0.8.10+commit.fc410830.Emscripten.clang Contract: TodoList √ should deploy successfully √ should revert if ... √ should lists tasks (206ms) 3 passing (329ms) 🎊🎉🎉🚀🚀🦄🦄🎊🎉🎉🚀🚀🦄🦄🎊🎉🎉🚀🚀🦄🦄🎊🎉🎉🚀🚀🦄 🦄BOOM YOU ARE BASICALLY A FULL BLOWN BLOCKCHAIN ENGINEER NOW🦄 🎊🎉🎉🚀🚀🦄🦄🎊🎉🎉🚀🚀🦄🦄🎊🎉🎉🚀🚀🦄🦄🎊🎉🎉🚀🚀🦄 erwan-hesry-WPTHZkA-M4I-unsplash.jpg Recap Testing is important All jokes aside, it really is. You should absolutely test your smart contracts before deploying them into production. There is a reason all those test networks exist! This is by no means even remotely comprehensive and, tbh, it barely even scratches the surface of what's needed and involved for good testing Looking for the code? 👉 github.com/frankTurtle Picture Credits Photo by Braden Collum on Unsplash Photo by Johan Godínez on Unsplash Photo by Erwan Hesry on Unsplash

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