I'm trying to unit test a private method that I have attached to my FileSystemWatcher's Error event. MSDN says that this event "occurs when the internal buffer overflows." I've tried to cause a buffer overflow but have not been successful so far. The FileSystemWatcher's various properties are: fileWatcher.IncludeSubdirectories = false; fileWatcher.Filter = "*"; fileWatcher.NotifyFilter = (NotifyFilters.FileName | NotifyFilters.LastAccess | NotifyFilters.Size); What is the best way of raising this event for the purpose of unit-testing?