Incorrectly named testfiles

[ghost]

Describe the bug

I'm seeing some inconsistencies with the names of some of the test files. Documenting it now to investigate later.

https://github.com/blockchain-certificates/cert-verifier-js/blob/master/test/fixtures/mainnet-invalid-merkle-receipt-2.0.json : says mainnet but checks against bitcoin testnet. There is no chain specified in the certificate.

https://github.com/blockchain-certificates/cert-verifier-js/blob/master/test/fixtures/mainnet-merkle-root-unmatch-2.0.json : says mainnet but checks against bitcoin testnet. There is no chain specified in the certificate.

https://raw.githubusercontent.com/blockchain-certificates/cert-verifier-js/master/test/fixtures/mainnet-revoked-2.0.json : says mainnet but checks against bitcoin testnet. There is no chain specified in the certificate.

https://raw.githubusercontent.com/blockchain-certificates/cert-verifier-js/master/test/fixtures/mainnet-valid-2.0-alpha.json : says mainnet but checks against bitcoin testnet. There is no chain specified in the certificate.

https://raw.githubusercontent.com/blockchain-certificates/cert-verifier-js/master/test/fixtures/testnet-404-issuer-url-1.2.json : says testnet but checks against bitcoin mainnet. There is no chain specified in the certificate.

To Reproduce
Steps to reproduce the behavior:

1. Put each of these certs into blockcerts.org

Expected behavior

Mainnet files should say/check mainnet, testnet files should say/check testnet.

Additional context

It appears that when chain is not specified, it checks against the address prefix? Not the best logic, but in either case it looks like these files are named incorrectly.