_Follow along with the video:_ --- ### Notes on Invariants We've already done a tonne and I know at times these concepts can be confusing, but we've seen first hand how powerful a fuzzing tool can be in breaking protocol invariants I briefly mentioned at the end of the last lesson the concept of baking invariants into protocols known as FREI-PI. I think it's important to see what can happen when these considerations aren't made and there's a great [**case study on Euler**](https://www.youtube.com/watch?v=vleHZqDc48M) available by `Tincho` that you should take a moment to watch now. It'll teach you a great deal about the importance of invariants. ### Additional Tools and Tests We exclusively used Foundry in our fuzzing so far, but there are other fuzzing tools available that we didn't go over which are worth checking out. - [**Echidna**](https://github.com/crytic/echidna) - Echidna is a Haskell program designed for fuzzing/property-based testing of Ethereum smart contracts. It uses sophisticated grammar-based fuzzing campaigns based on a contract ABI to falsify user-defined predicates or Solidity assertions. - [**Consensys**](https://diligence.us.auth0.com/login?state=hKFo2SBWT0JUTlRLR1FUUFM1VHFQNVR0Yi1ISWdNMmJCUGFhLaFupWxvZ2luo3RpZNkgUERzWTI1Wkg1bEM0VkMydFFYeG5vcy1fU0dGNjRiN0-jY2lk2SAxdzMzMGc3U1RUUmZFTk9ROHRBSXBPSzhLTTl3ZmdaZg&client=1w330g7STTRfENOQ8tAIpOK8KM9wfgZf&protocol=oauth2&scope=openid%20profile%20email%20read%3Acurrent_user%20enroll%20read%3Aauthenticators%20remove%3Aauthenticators%20offline_access&audience=https%3A%2F%2Ffaas.diligence.tools%2F&redirect_uri=https%3A%2F%2Ffuzzing.diligence.tools&screen_hint=signup&response_type=code&response_mode=query&nonce=fm15RXE2UzNSdlZPS0kyRW5UMkhJalVhM0dUUm5VLVNBUm4xWXhhd2pIZg%3D%3D&code_challenge=06fBFH8ZcFjUxLtj3KtOjpiD_AwxeoWmocBoQFhuEhQ&code_challenge_method=S256&auth0Client=eyJuYW1lIjoiYXV0aDAtcmVhY3QiLCJ2ZXJzaW9uIjoiMS4xMi4xIn0%3D) - Fuzzing as a service, so to speak. This is paid access only, so we won't be covering it here. - **Mutation Testing** - not something we'll cover in this course, but there's a link to more information and things you can try [**here**](https://github.com/Cyfrin/5-t-swap-audit/blob/audit-data/test/mutation/notes.md). Essentially this employs changing parts of the code to see if it breaks tests. - **Differential Testing** - comparative testing vs different iterations of the same code. We'll cover this in more detail in future. Another thing you might want to try is using [**Solodit**](https://solodit.xyz/) to research Weird ERC20s and how they've been identified in previous audits. Let's get on to some manual review now!
Follow along with the video:
We've already done a tonne and I know at times these concepts can be confusing, but we've seen first hand how powerful a fuzzing tool can be in breaking protocol invariants
I briefly mentioned at the end of the last lesson the concept of baking invariants into protocols known as FREI-PI. I think it's important to see what can happen when these considerations aren't made and there's a great case study on Euler available by Tincho that you should take a moment to watch now. It'll teach you a great deal about the importance of invariants.
We exclusively used Foundry in our fuzzing so far, but there are other fuzzing tools available that we didn't go over which are worth checking out.
Echidna - Echidna is a Haskell program designed for fuzzing/property-based testing of Ethereum smart contracts. It uses sophisticated grammar-based fuzzing campaigns based on a contract ABI to falsify user-defined predicates or Solidity assertions.
Consensys - Fuzzing as a service, so to speak. This is paid access only, so we won't be covering it here.
Mutation Testing - not something we'll cover in this course, but there's a link to more information and things you can try here. Essentially this employs changing parts of the code to see if it breaks tests.
Differential Testing - comparative testing vs different iterations of the same code. We'll cover this in more detail in future.
Another thing you might want to try is using Solodit to research Weird ERC20s and how they've been identified in previous audits.
Let's get on to some manual review now!
Covers security tools like fuzzing, Echidna, and mutation/diff testing to detect issues stresses the importance of testing & learning from history.