如何对文本显示在屏幕中央进行单元测试？

Question

This is a little script in go.

package bashutil

import (
    "fmt"
    "github.com/nsf/termbox-go"
)

func Center(s string) {
    if err := termbox.Init(); err != nil {
        panic(err)
    }
    w, _ := termbox.Size()
    termbox.Close()
    fmt.Printf(
        fmt.Sprintf("%%-%ds", w/2),
        fmt.Sprintf(fmt.Sprintf("%%%ds", w/2+len(s)/2), s),
    )
}

Can I unit test it? How can I test it? I think is a nonsense test a snippet so little. But, ... What if I would test this code? How can I test that an output is equals as I expect?

Can I test that fmt prints something like I expect?

Answer 1

What means "test" ?

I think "test" need have effect on output of a function.

Your function's output is Stdout, so we need get the output first.

We can do this simply:

func TestCenter(*testing.T) {
    stdoutBak := os.Stdout
    r, w, _ := os.Pipe()
    os.Stdout = w

    Center("hello")
    w.Close()
    os.Stdout = stdoutBak

    // Check output as a byte array
    outstr, _ := ioutil.ReadAll(r)
    fmt.Printf("%s", outstr)
}

Thus, you can check output format, spelling, etc.