EPIC: Test the framework

[laurentsenta]

We already have a few unit-tests in the framework, but coverage is low

ETA: 2024-12-01

- [ ] measure test coverage
- [ ] look into cassettes(related: https://github.com/vcr/vcr)
- [ ] look into the randomizer proxy (https://github.com/ipfs/gateway-conformance/pull/29)