Should I write unit test for everything?

Question

I am wondering should I write unit test for everything. There are some classes is very difficult to write unit test. For example, I am writing some program for handling audi

Answer 1

I only write unit tests where I know it saves me time. When I started out unit-testing this was only a small percentage of the classes (those awful ejb's!!). Today I test almost everything and I save total development time on every single thing I do. If there was an efficient way of testing user input through a microphone I'd do it too. But as far as I know, it's not possible in a manner that saves me time.

So i think you should unit test everything that is in your current "test capability". You should try to stretch this capability, but overreaching really sends signals of wrong priorities; In all likelihood there's some other test that deserves your attention more. (Technically I'm test infected but not TDD infected)

The law of diminishing returns applies to unit testing as much as any other testing; your payback on that last 5% is very low and the cost is high.