2.8 KiB
echidna
Echidna is a weird creature that eats bugs and is highly electrosensitive (with apologies to Jacob Stanley)
More seriously, it's a Haskell library designed for fuzzing/property based testing of EVM code. Currently it is quite alpha, and the API isn't guaranteed to be functional, let alone stable. It supports relatively sophisticated grammar-based fuzzing campaigns to falsify a variety of predicates.
Installation
stack is highly recommended to install echidna. If you are a particularly opinionated experienced Haskell user, cabal or hpack should work, but they are neither officially supported nor tested.
solc is the only echidna dependency not handled via stack. It is technically optional, but working with solidity source will fail without it.
Once solc is installed, installing stack and running stack upgrade; stack setup; stack install should be all that's needed.
Notably, if you are using stack, stack ghci will set up a REPL with all functions in scope.
This can be quite useful for playing around with the library.
Usage
echidna is actively being developed with more or less no regard for stability. As a result of this, there is a lack of extensive documentation at the present time. There is a small working example provided that should be relatively instructional.
Echidna.ABI
This module provides Hedgehog generators for most of the EVM ABI. It can be used without any other module to provide random "ASTs" (e.g. a random dynamic array of static arrays of 16 248-bit unsigned ints) or calldata (EVM-encoded function calls with these arguments).
Whenever possible, it tries to copy the convention of hevm.
Echidna.Exec
This module provides functionality for executing fuzzing campaigns.
fuzz executes a fuzzing campaign to check for a given predicate.
Its arguments are annotated in the source.
Notably, the predicates are specified to be compatible with hevm's Case type (just use checkExpectation).
Should neither that nor writing a predicate by hand suffice for checking some invariant, solPredicate is also provided for hotloading solidity contracts with more sophisticated predicates.
solPredicate is currently not practical for real usage though, as it runs solc once per invocation.
Echidna.Solidity
This module provides loadSolidity, which takes a solidity source file and provides a VM with the first contract therein loaded as well as a fuzz-compatible ABI definition.
At the moment, it is only compatible with single-contract solidity files, though if given a multi-contract file it will load the first and print a warning.
Questions/complaints/etc.
Leave an issue or shoot me a line at jp@trailofbits.com