SftpClient.OpenAsync should return Stream for ease of mocking

[doxxx]

SftpClient.OpenAsync currently returns an SftpFileStream which cannot be mocked by NSubstitute or even faked because it has private/internal constructors.

It would be nice if OpenAsync was instead defined as returning Stream, even though it actually returns a SftpFileStream. The only non-Stream public member that I can see is the Timeout property. If it's absolutely vital that this property is exposed, maybe define an ISftpFileStream interface instead? Or the timeout could be passed to OpenAsync.

[waldemarsson]

Any update on this? Trying to write unit tests for my integration and am stuck because I can't mock OpenAsync

[waldemarsson]

As a workaround I just created a proxy service that wraps ISftpClient.

internal class SftpClientProxy : IDisposable
{
    private readonly ISftpClient _sftpClient;

    public SftpClientProxy(ISftpClient sftpClient) => _sftpClient = sftpClient;

    public virtual async Task ConnectAsync(CancellationToken cancellationToken) =>
        await _sftpClient.ConnectAsync(cancellationToken);

    public virtual async Task<Stream> OpenAsync(string path, CancellationToken cancellationToken) =>
        await _sftpClient.OpenAsync(path, FileMode.Open, FileAccess.Read, cancellationToken);

    public void Dispose() => _sftpClient.Dispose();
}