Creating unit tests using I / O?

Question

Should I create unit tests using IO? Those. testing a class method for serializing / deserializing another object?

Answer 1

Yes - When you write unit tests for code that runs IO.

No - When you write unit tests for code that calls the methods you just tested above.

I would tag the first test suite with the xUnit category / tag labeled "Slow" or some such tag and run them less often. Over time, they will significantly slow down the time it takes to run your automated test suite. Therefore, simplify the exclusion of slow tests, => feedback from developers remains close to instantaneous, and the build server runs slow tests along with the rest at each registration. If it really takes a long time, then you can run the Slow tests every night or so.