public void Setup()
{
_fileSystem = new MemoryFileSystem().WithDrives("c:", "d:");
_emptyDrive = _fileSystem.DriveDescribing("d:");
_nonExistingDrive = _fileSystem.DriveDescribing("e:");
_nonExistingDirectory = _fileSystem.DirectoryDescribing(@"c:\nonExistingDirectory");
var populate = new FileSystemBuilder(_fileSystem);
_emptyDirectory = populate.WithDir(@"c:\emptyDirectory");
_nonEmptyDirectory = populate.WithDir(@"c:\crowdedDirectory");
populate.WithDir(@"c:\crowdedDirectory\first");
populate.WithDir(@"c:\crowdedDirectory\first\first");
populate.WithDir(@"c:\crowdedDirectory\second");
}