The Goldfinch Protocol and the Goldfinch Interface are thoroughly tested.
The test suites can be viewed in the open-source repo:
The test suites do not currently produce a code coverage report.
The Protocol's smart contracts have not undergone formal verification.
The Protocol's smart contracts are developed against extensive use of Ethereum mainnet, via so-called "mainnet forking". Deployment to Ethereum testnets is also used in development.