Using TDD to drive out thread-safe code

Question

What\'s a good way to leverage TDD to drive out thread-safe code? For example, say I have a factory method that utilizes lazy initialization to create only one instance of

Answer 1

When I test drove an implementation that needed to be thread safe recently I came up with the solution I provided as an answer for this question. Hope that helps even though there are no tests there. Hope link is OK raher than duplicating teh answer...