CleanFileCopier.cs

using System.IO.Abstractions;

public class CleanFileCopier
{
    private readonly IFileSystem _fileSystem;

    public CleanFileCopier(): this(new FileSystem())
    {
    }

    internal CleanFileCopier(IFileSystem fileSystem)
    {
        _fileSystem = fileSystem;
    }

    public void CopyFile(string sourceFilePath, string destinationDirectoryPath)
    {
        if (!_fileSystem.Directory.Exists(destinationDirectoryPath))
        {
            _fileSystem.Directory.CreateDirectory(destinationDirectoryPath);
        }

        var fileName = _fileSystem.Path.GetFileName(sourceFilePath);
        var destFileName = _fileSystem.Path.Combine(destinationDirectoryPath, fileName);
        _fileSystem.File.Copy(sourceFilePath, destFileName);
    }
}