How to test a function's output (stdout/stderr) in unit tests

Question

I have a simple function I want to test:

func (t *Thing) print(min_verbosity int, message string) {
    if t.verbosity >= minv {
        fmt.Print(message         


        

Answer 1

You could consider adding a return statement to your function to return the string that is actually printed out.

func (t *Thing) print(min_verbosity int, message string) string {
    if t.verbosity >= minv {
        fmt.Print(message)
        return message
    }
    return ""
}

Now, your test could just check the returned string against an expected string (rather than the print out). Maybe a bit more in-line with Test Driven Development (TDD).

And, in your production code, nothing would need to change, since you don't have to assign the return value of a function if you don't need it.