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Configure Your Local Environment

In this guide, we will go through the steps to set up a local development environment for building onchain integrations with Flow. We will use Foundry to install Flow as a dependency, and run a few simple tests.

At the end, you’ll have a development environment set up that you can use to build the rest of the examples under "Guides", or start your own integration project.

Pre-requisites​

You will need the following software on your machine:

In addition, familiarity with Ethereum and Solidity is requisite.

Set up using Flow integration template​

We put together a template repository that you can use to get started quickly. This repository features a basic project structure, pre-configured Flow imports, and a selection of sample contracts and tests.

tip

Make sure you are using the latest version of Foundry by running foundryup.

To install the template, simply execute the following commands:

$ mkdir flow-integration-template
$ cd flow-integration-template
$ forge init --template sablier-labs/flow-integration-template
$ bun install

Then, hop to the Run a Fork Test section to complete your set up and start developing.

Set up using Foundry template​

Foundry is a popular development toolkit for Ethereum projects, which we have used to build the Sablier Protocols. For the purposes of this guide, Foundry will provide us with the tooling needed to compile and test our contracts.

Let's use this command to spin up a new Foundry project:

$ forge init my-project
$ cd my-project
note

You might notice that the CLI is forge rather than foundry. This is because Foundry is a toolkit, and forge is just one of the tools that comes with it.

Once the initialization completes, take a look around at what got set up:

├── foundry.toml
├── script
├── src
└── test

The folder structure should be intuitive:

  • src is where you'll write Solidity contracts
  • test is where you'll write tests (also in Solidity)
  • script is where you'll write scripts to perform actions like deploying contracts (you guessed it, in Solidity)
  • foundry.toml is where you can configure your Foundry settings, which we will leave as is in this guide

Install Flow npm package​

Let's install the Flow Node.js packages using Bun:

$ bun add @sablier/flow

Bun will download the Flow contracts, along with their dependencies, and put them in the node_modules directory.

Let's remap the package names to point to the installed contracts. This step is required so that the Solidity compiler can find the Flow contracts when you import them:

$ echo "@sablier/flow=node_modules/@sablier/flow/" >> remappings.txt
$ echo "@openzeppelin/contracts/=node_modules/@openzeppelin/contracts/" >> remappings.txt
$ echo "@prb/math/=node_modules/@prb/math/" >> remappings.txt

That's it! You should now have a functional development environment to start building onchain Flow integrations. Let's run a quick test to confirm everything is set up properly.

Write your first contract​

Delete the src/Counter.sol and test/Counter.t.sol files generated by Forge, and create a new file: src/FlowStreamCreator.sol.

Paste the following code into src/FlowStreamCreator.sol.

Flow Stream Creator
loading...

Let's use Forge to compile this contract:

$ forge build

If the contract was compiled correctly, you should see this message:

[⠢] Compiling...
[⠰] Compiling { number } files with { compiler }
[⠒] Solc { compiler } finished in { time }
Compiler run successful
info

The minimum Solidity version supported by the Flow contracts is v0.8.22.

Run a fork test​

Foundry offers native support for running tests against a fork of Ethereum Mainnet, testnets and L2s, which is useful when building and testing integrations with onchain protocols like Sablier. In practice, this enables you to access all Sablier contracts deployed on Ethereum, and use them for testing your integration.

As a prerequisite, you will need an RPC that supports forking. A good solution for this is Alchemy, as it includes forking in its free tier plan.

Once you have obtained your RPC, you can proceed to run the following test:

Stream Creator Test
loading...

You can run the test using Forge:

$ forge test

If the test passed, you should see a message like this:

Ran 2 tests for test/FlowStreamCreator.t.sol:FlowStreamCreatorTest
[PASS] test_CreateFlowStream() (gas: 147915)
[PASS] test_CreateFlowStreamAndDeposit() (gas: 224823)
Suite result: ok. 2 passed; 0 failed; 0 skipped; finished in 986.20ms (4.16ms CPU time)

Next steps​

Congratulations! Your environment is now configured, and you are prepared to start building. Explore the guides section to discover various Flow features available for integration. Remember to include all contracts (.sol files) in thesrc folder and their corresponding tests in the test folder.

As far as Foundry is concerned, there is much more to uncover. If you want to learn more about it, check out the Foundry Book, which contains numerous examples and tutorials. A deep understanding of Foundry will enable you to create more sophisticated integrations with Flow.