`bitcoin.conf`:
```
...
testnet=1
# [wallets]
test.wallet=test_alpha
test.wallet=alpha_wallet
test.wallet=none
...
```

Run bitcoin client.

`debug.log`:
```
...
2019-02-03T13:09:23Z Using wallet directory /home/hebasto/.bitcoin/testnet3/wallets
2019-02-03T13:09:23Z init message: Verifying wallet(s)...
2019-02-03T13:09:23Z Using BerkeleyDB version Berkeley DB 4.8.30: (April  9, 2010)
2019-02-03T13:09:23Z Using wallet wallet.dat
2019-02-03T13:09:23Z BerkeleyEnvironment::Open: LogDir=/home/hebasto/.bitcoin/testnet3/wallets/test_alpha/database ErrorFile=/home/hebasto/.bitcoin/testnet3/wallets/test_alpha/db.log
2019-02-03T13:09:23Z Using BerkeleyDB version Berkeley DB 4.8.30: (April  9, 2010)
2019-02-03T13:09:23Z Using wallet wallet.dat
2019-02-03T13:09:23Z BerkeleyEnvironment::Open: LogDir=/home/hebasto/.bitcoin/testnet3/wallets/alpha_wallet/database ErrorFile=/home/hebasto/.bitcoin/testnet3/wallets/alpha_wallet/db.log
2019-02-03T13:09:23Z Using BerkeleyDB version Berkeley DB 4.8.30: (April  9, 2010)
2019-02-03T13:09:23Z Using wallet wallet.dat
2019-02-03T13:09:23Z BerkeleyEnvironment::Open: LogDir=/home/hebasto/.bitcoin/testnet3/wallets/none/database ErrorFile=/home/hebasto/.bitcoin/testnet3/wallets/none/db.log9
...
```

In multi-wallet environment a wallet database file reference (`wallet.dat`) without a wallet name (e.g., `test_alpha`) could be confusing.
{
    if (env.IsMock()) return;
    int ret = db.get_mpf()->get_fileid(fileid.value);
    if (ret != 0) {
        throw std::runtime_error(strprintf("BerkeleyBatch: Can't open database %s (get_fileid failed with %d)", filename, ret));
    }
    for (const auto& item : env.m_fileids) {
        if (fileid == item.second && &fileid != &item.second) {
            throw std::runtime_error(strprintf("BerkeleyBatch: Can't open database %s (duplicates fileid %s from %s)", filename,
                HexStr(std::begin(item.second.value), std::end(item.second.value)), item.first));
        }
    }
}
CCriticalSection cs_db;
std::map<std::string, std::weak_ptr<BerkeleyEnvironment>> g_dbenvs GUARDED_BY(cs_db); 
} 
bool WalletDatabaseFileId::operator==(const WalletDatabaseFileId& rhs) const