Readline Failed in Go Test Case - go

Question

I'm experimenting getting keyboard input in a test case, basically I followed this example,
https://www.socketloop.com/tutorials/golang-read-input-from-console-line
and in my unit test case, it always result in error of "EOF" without giving me a chance to type in from keyboard.
Is there any special in Go unit test environment? Or I should look into another better option?
My code looks like,
func (o *Player) consoleReadLn() (line string) {
consoleReader := bufio.NewReader(os.Stdin)
line, err := consoleReader.ReadString('\n')
if err != nil {
panic(err.Error()) // it just panic: EOF
}
return
}

Answer 1

Firstly, your code should be corrected to:
import "testing/iotest"
func (o *Player) consoleReadLn() string {
consoleReader := bufio.NewReader(os.Stdin)
s := ""
for {
s1, err := consoleReader.ReadString('\n')
if err == io.EOF {
break
}
if err != nil && err != iotest.ErrTimeout {
panic("GetLines: " + err.Error())
}
s += s1
}
return s
}
Because you expect using \n as delimiter of a line of string, so it will return the data with EOF which is \n in Unix OS, see godoc bufio#Reader.ReadString:
ReadString reads until the first occurrence of delim in the input, returning a string containing the data up to and including the delimiter. If ReadString encounters an error before finding a delimiter, it returns the data read before the error and the error itself (often io.EOF). ReadString returns err != nil if and only if the returned data does not end in delim. For simple uses, a Scanner may be more convenient.
However, I suggest reading this answer Read from initial stdin in GO?
Secondly, it is hard to test STDIN in unit test context like go test. I found this mail saying:
the new go test runs tests with standard input connected
to /dev/null.
So I think it is hard to test os.Stdin via go test directly, for example, the following code confirmed it doesn't read /dev/stdin at all when running command echo this is stdin | go test ./:
import "io/ioutil"
import "testing"
import "fmt"
func TestSTDIN(t *testing.T) {
bytes, err := ioutil.ReadAll(os.Stdin)
if err != nil {
t.Fatal(err)
}
fmt.Println(string(bytes))
}