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2.1.0-rc.0 • Public • Published

Nomad Bridge

Solidity implementations of the Nomad Bridge.


  • yarn bootstrap: yarn clean and yarn build


  • yarn build: compile smart contracts and create definitions for the SDK


For testing, we use Foundry.

  • Run yarn build:accumulator-cli from the root directory of the monorepo. It will build a rust-based cli tool that creates Sparse Merkle Tree proofs for arbitrary data. It's used in our testing suite via the --ffi flag for Forge. The binary is built in there /scripts top-level directory of the monorepo
  • --ffi means that Forge will run arbitrary shell commands as part of the testing suite. You should never run forge --ffi without knowing what exactly are the shell commands that will be executed, as the testing suite could be malicious and execute malicious commands. This is why the feature is disabled by default and must be explicitly enabled.
  • yarn test:unit will run all unit tests. Note that --ffi is enabled by default,
  • yarn snapshot will create a new .gas-snapshot. You can inspect the different gas usage via git diff
  • 'yarn snapshot:check' will run the test suite and check gas consumption against the existing .gas-snapshot. It will pass only if there is no change in the gas consumption
  • yarn gen-proof will execute the accumulator-cli binary

Suggested workflow

  • Define feature
  • Write tests based on Foundry best practices and the existing test structure
  • Run test suite with FOUNDRY_PROFILE=bridge forge test --ffi -vvv and verify that your new tests FAIL
  • Write the new feature
  • Run again the test suite and verify that the tests PASS
  • Run yarn snapshot to produce the new gas snapshot. You can't use yarn snapshot:check, since you added new tests that are not present in the current .gas-snapshot. Gas snapshots showcase how much gas your tests consume and are useful to serve as a benchmark for the gas consumption of your code. As you write new features and/or refactor your code, the gas snapshot can change, illustrating where your changes affected the already defined codepaths. You can read more about gas snapshots on the Foyndry book
  • Run yarn storage-inspect:check to see if the storage layout of the smart contracts have changed. If it has, this could potentially create problems in the upgrade process. If the new layout is correct, run yarn storage-inspect:generate to create a new layout file (replacing the old one) and commit the new file. If we don't commit the new layout, the CI will fail.

Tip: It is advised to run the forge commands on their own and not via yarn or npm for faster development cycle. yarn will add a few seconds of lag, due to the fact that it has to spin up a Node runtime and the interpret the yarn source code.

Static Analysis

We suggest all contributors to use slither while developing, to avoid common mistakes.

  • Install Slither
  • Run yarn test:static-analyze

We use a yarn command because we need to link the top-level node_modules directory in the bridge-contracts package. It's a known issue for which the workaround is to link the directory.


The NFT Accountant is a system for recording unbridging events on Ethereum.

Users receive an NFT representing the amount being unbridged. Users can use this NFT to recover funds on a continual basis.




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npm i @nomad-xyz/contracts-bridge

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  • rswanson
  • annascarroll
  • prestwich
  • erinhales