created_at2024-02-09 00:03:02.297033
updated_at2024-04-26 22:38:15.874819
descriptionArbiter macros for Ethereum smart contract testing.
Waylon Jepsen (0xJepsen)




Expanding the EVM tooling ecosystem.

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Arbiter is a blazing-fast Ethereum sandbox that lets developers orchestrate event-driven simulations. The framework allows for fine-grained control over a (Rust) Ethereum Virtual Machine (EVM) to provide stateful Ethereum smart-contract interactions and the creation of behaviors that can be coalesced into complex scenarios or automation. We use ethers-rs middleware on top of revm, which is used in ETH clients such as reth as well as foundry. This gives us speed, configurability, and modularity that feels like a lightweight custom Ethereum node.

The primary use of Arbiter is to probe the mechanism security of smart contracts. If this interests you, please see the Vulnerability Corpus.

The Arbiter workspace has five crates:

  • arbiter: The bin that exposes a command line interface for forking and binding contracts.

  • arbiter-core: A lib containing the core logic for the Arbiter framework, including the ArbiterMiddleware discussed before, and the Environment, our sandbox.

  • arbiter-engine: A lib that provides abstractions for building simulations, agents, and behaviors.

  • arbiter-macros: A lib crate that contains the macros used to simplify development with Arbiter.

  • arbiter-bindings: A lib crate containing bindings for utility smart contracts used for testing and development.


Here you can find the Arbiter Documentation. This is an mdbook that provides higher level understanding of how to use the entirety of the Arbiter framework.


Arbiter was built to allow you to work with smart contracts in a stateful sandbox and design agents that can be used alongside the contracts. This gives you many capabilities. For instance, smart contract engineers must test their contracts against various potentially adversarial environments and parameters and not rely on static stateless testing.

In Decentralized Finance (DeFi), a wide array of complex decentralized applications can use the testing described above. Still, implicit financial strategies also encompass many agents and parameterizations. A financial engineer may want to test their strategies against thousands of market conditions, contract settings, shocks, and autonomous or random AI agents while ensuring their approach isn't vulnerable to bytecode-level exploits. Likewise, the same engineer may want to develop searcher agents, solver agents, or other autonomous agents that can be run on the blockchain.

Working with the Arbiter Framework

To work with Arbiter, you must have Rust installed on your machine. You can install Rust by following the instructions here. It will also be helpful to get the cargo-generate package, which you can install by doing:

cargo install cargo-generate


We have an example that will run what we have set up in a template. To run this, you can clone the repository and update the submodules:

git clone
cd arbiter
git submodule update --init --recursive

From here, you can now try running the following from the clone's root directory:

cargo run --example template 

This command will enter the template CLI and show you the commands and flags.

To run the ModifiedCounter.sol example and see some logging, try:

cargo run --example template simulate examples/template/configs/example.toml -vvv

This sets the log level to debug so you can see what's happening internally.


To create your own Arbiter project off of our template arbiter-template, you can run the following:

cd <your/chosen/directory>
cargo generate

You'll be prompted to provide a project name, and the rest will be set up for you!


To install the Arbiter binary, run:

cargo install arbiter

This will install the Arbiter binary on your machine. You can then run arbiter --help to see that Arbiter was correctly installed and see the help menu.


You can load or write your own smart contracts in the contracts/ directory of your templated project and begin writing your own simulations. Arbiter treats Rust smart-contract bindings as first-class citizens. The contract bindings are generated via Foundry's forge command. arbiter bind wraps forge with convenience features that generate all your bindings to src/bindings as a Rust module. Foundry power-users can use forge directly.


To fork a state of an EVM network, you must first create a fork config file. An example is provided in the examples/fork directory. Essentially, you provide your storage location for the data, the network you want, the block number you want, and metadata about the contracts you want to fork.

arbiter fork <fork_config.toml>

This will create a fork of the network you specified in the config file and store it in your specified location. It can then be loaded into an arbiter-core Environment using the Fork::from_disk() method.

Forking is done this way to ensure that all emulation does not require a constant connection to an RPC endpoint. You may find that Anvil has a more accessible forking interface. However, an online forking mechanism makes RPC calls to update the state as necessary. Arbiter Environment forking is for creating a state, storing it locally, and being able to initialize a simulation from that state when desired. We plan to allow arbiter-engine to integrate with other network types, such as Anvil, in the future!

Optional Arguments You can run arbiter fork <fork_config.toml> --overwrite to overwrite the fork if it already exists.

Cargo Docs

To see the Cargo docs for the Arbiter crates, please visit the following:

You will find each of these on


In arbiter-core, we have a a small benchmarking suite that compares the ArbiterMiddleware implementation over the Environment to the Anvil local testnet chain implementation. The biggest reasons we chose to build Arbiter was to gain more control over the EVM environment and to have a more robust simulation framework. Still, we also wanted to gain speed, so we chose to build our own interface over revm instead of using Anvil (which uses revm under the hood). For the following, Anvil was set to mine blocks for each transaction instead of setting an enforced block time. The Environment was configured with a block rate of 10.0. Preliminary benchmarks of the ArbiterMiddleware interface over revm against Anvil are given in the following table.

To run the benchmarking code yourself, you can run:

cargo bench --package arbiter-core
Operation ArbiterMiddleware Anvil Relative Difference
Deploy 238.975µs 7712.436µs ~32.2729x
Lookup 565.617µs 17880.124µs ~31.6117x
Stateless Call 1402.524µs 10397.55µs ~7.413456x
Stateful Call 2043.88µs 154553.225µs ~75.61756x

The above can be described by:

  • Deploy: Deploying a contract to the EVM. In this method, we deployed both ArbiterToken and ArbiterMath, so you can divide the time by two to estimate the time it takes to deploy a single contract.

  • Lookup: Look up the balanceOf for a client's address for ArbiterToken. In this method, we called ArbiterToken's balanceOf function 100 times. Divide by 100 to get the time to look up a single balance.

  • Stateless Call: Calling a contract that does not mutate state. In this method, we called ArbiterMath's cdf function 100 times. Divide by 100 to get the time to call a single stateless function.

  • Stateful Call: Calling a contract that mutates state. In this call, we called ArbiterToken's mint function 100 times. Divide by 100 to get the time to call a single stateful function.

The benchmarking code can be found in the arbiter-core/benches/ directory, and these specific times were achieved over a 1000 run average. The above was achieved by running cargo bench --package arbiter-core, which will automatically run with the release profile. Times were achieved on an Apple Macbook Pro M1 Max with 8 performance and 2 efficiency cores and 32GB of RAM.

Of course, the use cases of Anvil and the ArbiterMiddleware can be different. Anvil represents a more realistic environment with networking and mining. At the same time, the ArbiterMiddleware is a simpler environment with the bare essentials to running stateful simulations. Anvil also mines blocks for each transaction, while the ArbiterMiddleware does not.

Please let us know if you need any help with these benchmarks or suggestions for improving them!


If you contribute, please write tests for any new code you write. To run the tests, you can run the following:

cargo test --all --all-features


See our Contributing Guidelines

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cargo fmt