Why fmt.Scan doesn't wait input while using in testing?

[Googol Lee]

I try to use fmt.Scan to get user input when running testing. Code
like below:

package sample

import (
"testing"
"fmt"
)

func TestSomething(t *testing.T) {
var input string
fmt.Scan(&input)
fmt.Println(input)
}

But fmt.Scan doesn't work. It return empty string immediately after
call. Is there a way to get user input when running testing?

Thanks.

[Dustin]

On Friday, February 17, 2012 8:07:34 PM UTC-8, Googol Lee wrote:

func TestSomething(t *testing.T) {
  var input string
  fmt.Scan(&input)
  fmt.Println(input)
}

But fmt.Scan doesn't work. It return empty string immediately after
call. Is there a way to get user input when running testing?

  Tests run with /dev/null on console.  You should really check the results of those calls.  :)

[Evan Shaw]

fmt.Scan reads from os.Stdin, which is set to /dev/null when testing.
Tests should be automated and self-contained anyway, so you don't want
to read from stdin.

Either use an external file, a bytes.Buffer, or a strings.Reader and
call scan.Fscan if you want to scan something.

- Evan

[Kyle Lemons]

You should also check error returns when scanning.

[Googol Lee]

Got it. Thanks :)

[ashinmi...@gmail.com]

Hello Evan, where is this `set to /dev/null` operating in the source code of golang? I tried to explore it, but I didn't find it

在 2012年2月18日星期六 UTC+8下午12:16:48，Evan Shaw写道：

[Ian Lance Taylor]

On Fri, Mar 27, 2020 at 10:29 PM <ashinmi...@gmail.com> wrote:
>
> Hello Evan, where is this `set to /dev/null` operating in the source code of golang? I tried to explore it, but I didn't find it

You are replying to a message from 2012. Many things have changed since then.

Ian

> 在 2012年2月18日星期六 UTC+8下午12:16:48，Evan Shaw写道：
>>
>> fmt.Scan reads from os.Stdin, which is set to /dev/null when testing.
>> Tests should be automated and self-contained anyway, so you don't want
>> to read from stdin.
>>
>> Either use an external file, a bytes.Buffer, or a strings.Reader and
>> call scan.Fscan if you want to scan something.
>>
>> - Evan
>

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