How to Setup Foundry and Write a Basic Unit Test

Learn how to set up Foundry and use the Forge command-line tool to run your smart contract tests written in Solidity.

What you will accomplish

Prerequisites

Before you begin, you should be familiar with the following:

Also, you should have the following set up on your computer ⬇
Check your prerequisites set up ⬇

Open your terminal, and enter the following commands.

git --version
code --version
node --version
npm --version

Ensure these versions meet or exceed the minimum requirements:

git --version
git version 2.39.2 (Apple Git-143)

code --version
1.81.1
6c3e3dba23e8fadc360aed75ce363ba185c49794
arm64

node --version
v20.6.1

npm --version
9.8.1

Get started

Set up project

To follow along, start with the main branch, which is the default branch of this repository. This gives you the initial state from which you can follow along with the steps as described in the tutorial.

git clone git@github.com:hedera-dev/setup-foundry-and-write-basic-unit-test.git

Add a submodule

Forge manages dependencies by using git submodules. Run the steps below to add and install the git submodules necessary to use Forge.

Next, add the Forge Standard Library to your project:

cd setup-foundry-and-write-basic-unit-test
git submodule add https://github.com/foundry-rs/forge-std lib/forge-std

This command will add the forge standard library to our project by creating a folder named lib. The forge standard library is the preferred testing library when working with Foundry.

Install Foundryup

Foundryup represents Foundry's tool management approach. Executing this command will install forge and other essential Foundry CLI tools.

curl -L https://foundry.paradigm.xyz | bash

You should see output similar to the following:

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
100  1942  100  1942    0     0   3336      0 --:--:-- --:--:-- --:--:--     0
Installing foundryup...
######################################################################## 100.0%

Detected your preferred shell is zsh and added foundryup to PATH. Run 'source /Users/abi/.zshenv' or start a new terminal session to use foundryup.
Then, simply run 'foundryup' to install Foundry.

You may need to add foundry to PATH and open a new terminal to make the foundryup command available. Then run foundryup to install Foundry.

Once you've installed foundry you should get a similar output
xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx
 ╔═╗ ╔═╗ ╦ ╦ ╔╗╔ ╔╦╗ ╦═╗ ╦ ╦         Portable and modular toolkit
 ╠╣  ║ ║ ║ ║ ║║║  ║║ ╠╦╝ ╚╦╝    for Ethereum Application Development
 ╚   ╚═╝ ╚═╝ ╝╚╝ ═╩╝ ╩╚═  ╩                 written in Rust.
.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx
Repo       : https://github.com/foundry-rs/
Book       : https://book.getfoundry.sh/                      
Chat       : https://t.me/foundry_rs/                         
Support    : https://t.me/foundry_support/
Contribute : https://github.com/orgs/foundry-rs/projects/2/
.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx
foundryup: installing foundry (version nightly, tag nightly)
foundryup: downloading latest forge, cast, anvil, and chisel
######################################################################### 100.0%
foundryup: downloading manpages
######################################################################### 100.0%
foundryup: installed - forge 0.2.0 (5ea2c5e 2024-01-22T00:24:09.322705000Z)
foundryup: installed - cast 0.2.0 (5ea2c5e 2024-01-22T00:24:09.341247000Z)
foundryup: installed - anvil 0.2.0 (5ea2c5e 2024-01-22T00:24:09.359481000Z)
foundryup: installed - chisel 0.2.0 (5ea2c5e 2024-01-22T00:24:09.377345000Z)
foundryup: done!

Install the submodule dependencies

forge install

Remap dependencies

In order to make the import of the forge standard library easier to write, we will remap the dependency.

Open the project setup-foundry-and-write-basic-unit-test, in a code editor.

Create a new text file under the root directory named remappings.txt

Paste in the following line of code

forge-std/=lib/forge-std/src/

When we want to import from forge-std we will write: import "forge-std/Contract.sol"

Setup the test

A test file named TodoList.t.sol has been provided to you under the test folder.

On line 7, we see our TodoListTest contract inherits Forge Standard Library's Test contract, which provides us access to the necessary functionality to test our smart contracts.

Step 1: Create your test instance

Create an instance of the contract TodoList.sol in TodoList.t.sol order to be able to test it.

TodoList public todoList;

Look for a comment in the code to locate the specific lines of code that you will need to edit. For example, in this step, look for this: // Step (1) in the accompanying tutorial. You will need to delete the inline comment that looks like this: /* ... */. Replace it with the correct code.

Write a test

Step 2: Deploy a new contract every time you run a test

The setup() function is invoked before each test case is run and is optional. Have the TodoList.t.sol test contract deploy a new TodoList contract by adding the following code in the setUp() function.

todoList = new TodoList();

Step 3: Confirm that the number of todos increases by one after calling createTodo()

Assert that the numberOfTodosAfter executing createTodo() is equal to the numberOftodosBefore + 1.

     assertEq(numberOfTodosAfter, (numberOfTodosBefore + 1), "create todo test");

Build and run your test

Foundry expects the test keyword as a prefix to distinguish a test. Therefore, all tests you want to run must be prefixed with the test keyword.

Foundry expects the test keyword as a prefix to distinguiash a test. Therefore, all tests that you want to run must be prefixed with the test keyword.

In the terminal, ensure you are in the root project directory and build the project.

forge build

You should see output similar to the following:

[⠒] Compiling...
[⠔] Compiling 22 files with 0.8.23
[⠑] Solc 0.8.23 finished in 3.44s
Compiler run successful!

After a successful build, run your test.

forge test

You should see output similar to the following:

[⠢] Compiling...
No files changed, compilation skipped

Running 1 test for test/TodoList.t.sol:TodoListTest
[PASS] test_createTodo_returnsNumberOfTodosIncrementedByOne() (gas: 76346)
Test result: ok. 1 passed; 0 failed; 0 skipped; finished in 1.12ms
 
Ran 1 test suites: 1 tests passed, 0 failed, 0 skipped (1 total tests)

By default forge test only displays a minimal summary of a test, whether it failed or passed. You can display more detailed information by using the -v flag and increasing the verbosity.

In the terminal, re-run your test but include a verbosity level 4. This will display stack traces for all tests, including the setup.

forge test -vvvv
Level 4 verbosity output

Forge Gas Reports

Forge has functionality built in to give you gas reports of your contracts. You can specify which contract should generate a gas report in the foundry.toml file.

The foundry.toml file is a configuration file that is used to configure forge.

Create a new file in the root directory named foundry.toml. Paste the following contents.

[profile.default]
src = 'src'
out = 'out'
libs = ['lib']

# Step 4 - Configure foundry to produce a gas report for `TodoList.sol`
#/* ... */

[rpc_endpoints]
h_testnet = "https://testnet.hashio.io/api"
h_mainnet = "https://mainnet.hashio.io/api"

# See more config options https://github.com/foundry-rs/foundry/tree/master/config

Step 4: Configure foundry to produce a gas report for TodoList.sol

Replace the comment #/* ... */ with the line below:

gas_reports = ["TodoList"]

In the terminal, generate a gas report.

forge test --gas-report

You should see output similar to the following:

Your output will show you an estimated gas average, median, and max for each contract function used in a test and total deployment cost and size.

Complete

Congratulations, you have completed how to setup Foundry and write a basic unit test.

You have learned how to:

Writer: Abi Castro, DevRel Engineer

GitHub | Twitter

Editor: Brendan, DevRel Engineer

GitHub | Blog

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