To those who disagree with me. Testing was needed, and is reliable, not saying there is something in place that would have solved this particular instance but

To those who disagree with me. Testing was needed, and is reliable, not saying there is something in place that would have solved this particular instance but saying "not particularly reliable" means that you haven't properly addressed the problem. If you can't write a test that tells you your code works, then how can you as a human verify it passes all required cases manually reliably. YES, I have written tests in multi-threaded situations before. Your aversion to trying it doesn't make my statement wrong.