Are there example certificates (PEM format) for testing available somewhere ? For test purposes I would need a certificate signed with SHAS256/ECDSA P-256, together with a complete chain to test verification.
you can find some ECC certificates using crt.sh tool. For example DigiCert issues ECC certificates, if you narrow the search to this CA, you can manually search for certificates with P-256 curve.
Following filters searches for all certificates issued by DigiCert ECC Secure Server CA https://crt.sh/?Identity=%25&iCAID=1516