The hevm project is an implementation of the Ethereum virtual machine (EVM) made specifically for unit testing and debugging smart contracts. It is developed by DappHub and integrates especially well with the dapp tool suite. The hevm command line program can run unit tests, interactively debug contracts while showing the Solidity source, or run arbitrary EVM code.

This is not yet a complete EVM. For example, the precompiled contracts are missing. We do well on Ethereum's VMTests suite (see hevm v0.11.1 test report) but we can't guarantee exact consensus conformance. The precompiled contracts are entirely missing for now, and we're in the process of implementing the Metropolis EIPs.

Note: the hevm test runner and debugger currently assumes the use of the ds-test framework for Solidity unit tests and the dapp tool suite.

After running dapp build, you can run your unit test suite with

$ hevm dapp-test

or you can enter the interactive debugger using

$ hevm interactive

• Esc: exit debugger
• n: step by one instruction
• p: step backwards by one instruction
• N: step to the next source position
• C-n: step to the next source position and don't enter CALL or CREATE

DappHub maintains a repository for the Nix package manager, which works on any Linux distribution, OS X, and other Unix-likes.

These commands will install Nix, add the DappHub "channel", and install hevm. The channel has cached binaries for Linux and OS X.

$ curl https://nixos.org/nix/install | sh
$ nix-channel --add https://nix.dapphub.com/pkgs/dapphub
$ nix-channel --update
$ nix-env -iA dapphub.hevm

This Nix channel can also be used to install dapp, our development tool:

$ nix-env -iA dapphub.dapp

If you don't want to compile anything, and you're on x86-64 Linux, you can download a static binary from the "Releases" tab on GitHub. If the static binary complains about a "terminfo" file, you have to set the TERMINFO environment variable; on Ubuntu, you should do

$ export TERMINFO=/lib/terminfo

(Put that in your ~/.bashrc for convenience.)

If you can't or won't use Nix, the easiest way especially if you don't have GHC (the Haskell compiler) installed already, is to use Stack, which can take care of installing GHC for you. These commands should work:

$ curl -sSL https://get.haskellstack.org/ | sh
$ git clone https://github.com/dapphub/hevm
$ cd hevm && stack setup && stack install

If you prefer to use your own installation of GHC and the basic Haskell package manager, Cabal, simply run:

$ git clone https://github.com/dapphub/hevm
$ cd hevm && cabal configure && cabal install

You can find us in the DappHub chat at https://dapphub.chat/, especially the #dev channel.