When a replacement transaction doesn't meet the required price bump, Nethermind returns ReplacementNotAllowed while geth returns replacement transaction underpriced.

This was discovered while running taiko-client integration tests against both execution clients (more details on NethermindEth/surge-taiko-mono#245). We had to add a workaround to check for different error messages depending on which client is being used:

if os.Getenv("L2_NODE") == "l2_nmc" {
    s.Equal("ReplacementNotAllowed", err.Error())
} else {
    s.Equal("replacement transaction underpriced", err.Error())
}

It would be nice if Nethermind returned the same error message as geth for this case.

Where the difference comes from

Geth

In geth, the error is defined in core/txpool/errors.go:

// ErrReplaceUnderpriced is returned if a transaction is attempted to be replaced
// with a different one without the required price bump.
ErrReplaceUnderpriced = errors.New("replacement transaction underpriced")

Nethermind

In Nethermind, the result is defined in Nethermind.TxPool/AcceptTxResult.cs:

/// <summary>
/// Transaction is not allowed to replace the one already in the pool. Fee bump is too low or some requirements are not fulfilled
/// </summary>
public static readonly AcceptTxResult ReplacementNotAllowed = new(11, nameof(ReplacementNotAllowed));