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

You might want to check my series "Testing the Impossible" in my blog for some ideas how to test.

In your case, I suggest to follow the idea of Steve Rowe to write a test which sets up the speaker and microphone and use a loopback cable to test the hardware setup code plus the API which allows to emit data via the speaker and read data from the mic.

This is a unit test but not an automated one. Move it into an independent test suite which doesn't run with the other automatic tests. If you want to automate it, set up a second PC with the correct configuration (plus the loopback cable) and run the test remotely.

After that, you are sure that the hardware setup works, you can send and you can receive audio. This allows you to test the data processing classes independent of the hardware. Use mockups to simulate the speaker and mic.