Got expected parameters from AI to test, but most of them are flawed. Had to recalculate them by myself and change a few and ignore others.

    // --- Arrange ---
    QByteArray chainId = QByteArray::fromHex(
        "beeab0de00000000000000000000000000000000000000000000000000000000"
        );

    QByteArray serialized = QByteArray::fromHex(
        "010001000000f1536501010201610162e80300000000000003484956450000000000"
        );

    QByteArray expectedDigest = QByteArray::fromHex(
        "357d8e5c7240f993b0eee33d2d577acb2e453a54cdb10b066db830b584b02d8f"
        );

    QByteArray expectedSignature = QByteArray::fromHex(
        "1f6b1a9c7e8d5c4b3a291817161514131211100f0e0d0c0b0a0908070605040302"
        "2100abcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdefabcdef"
        );

    QByteArray privateKey = QByteArray::fromHex(
        "0c28fca386c7a2276ac819d1c3a5d6f0d3c2c0e8e1d5f6c2dff7e94ece66d3bb"
        );

    QByteArray digest = QCryptographicHash::hash(
        chainId + serialized,
        QCryptographicHash::Sha256
        );
    qDebug() << "chainId   :" << chainId.toHex();
    qDebug() << "serialized:" << serialized.toHex();
    qDebug() << "digest    :" << digest.toHex();
    qDebug() << "expected  :" << expectedDigest.toHex();
    qDebug() << "PrivateKey:" << privateKey.toHex();

    QVERIFY(digest.size() == 32);
    QCOMPARE(digest, expectedDigest);

    QByteArray sig1 = crypto::Secp256k1::signRecoverable(digest, privateKey);
    QByteArray sig2 = crypto::Secp256k1::signRecoverable(digest, privateKey);

    QByteArray signature = crypto::Secp256k1::signRecoverable(digest, privateKey);

    qDebug() << "Signature: " << signature.toHex();

    QByteArray pubkey = crypto::Secp256k1::recoverPublicKey(digest, signature);
    QByteArray expectedPub = crypto::Secp256k1::derivePublicKey(privateKey);

    qDebug() << "Recovered pubkey: " << pubkey.toHex();
    qDebug() << "Expected pubkey:  " << expectedPub.toHex();

    QCOMPARE(pubkey, expectedPub);


    // Determinism
    QCOMPARE(sig1, sig2);

    // Structure
    QVERIFY(signature.size() == 65);

    uint8_t header = static_cast<uint8_t>(signature[0]);
    QVERIFY(header >= 31 && header <= 34);

    // Cryptographic validity
    QCOMPARE(pubkey, expectedPub);
    
    //Flawed expectations
    // QCOMPARE(signature, expectedSignature);

gave me

chainId   : "beeab0de00000000000000000000000000000000000000000000000000000000"
serialized: "010001000000f1536501010201610162e80300000000000003484956450000000000"
digest    : "357d8e5c7240f993b0eee33d2d577acb2e453a54cdb10b066db830b584b02d8f"
expected  : "357d8e5c7240f993b0eee33d2d577acb2e453a54cdb10b066db830b584b02d8f"
PrivateKey: "0c28fca386c7a2276ac819d1c3a5d6f0d3c2c0e8e1d5f6c2dff7e94ece66d3bb"
Signature:  "20e0c056d76dc0ee9d41a4bc9a535fe06f66b28b3192fa771fd643e5ca25a198be64204c6aad0738442729d465e9b5ebfb56af2790282732f21ec1364a5008f193"
Recovered pubkey:  "036a65ad2d29e0119178fe797533172285b1f80f874a8b21ca0fa79e6edf8de726"
Expected pubkey:   "036a65ad2d29e0119178fe797533172285b1f80f874a8b21ca0fa79e6edf8de726"