Echidna is open source and one of the most used testing frameworks on the EVM ecosystem. It is used for fuzzing/property-based testing of Ethereum smart contracts. Echidna’s core features include:

– Support assertion checking,
– Custom property-checking,
– Estimation of maximum gas usage
– Slither integration to extract helpful information before the fuzzing campaign

Today, Echidna is an essential tool that security companies use to audit smart contracts.