GO attach stdin in test setup method

Question

I am using the built-in testing module to run some functional tests I have in my GO project. In my project I have external dependencies, which I connect to in my TestMain method. I save these connections to variables which then I use in the tests themselves, and the connections can take a long time to establish properly (Kafka anyone?). I would like to run the tests on-demand, but after these variables have been setup.

So what I want is to listen to stdin in my TestMain function and either run or quit the tests. But I want it to be controlled by the user so I can have my test environment setup, and the tests will run on my command.

But sadly, it seems that when running go test ... that stdin is mapped directly to /dev/null. So when I try to read os.Stdin I get an EOF error. The minimum code for this is:

package tests

import (
    "bufio"
    "fmt"
    "os"
    "testing"
)

func TestMain(m *testing.M) {
    reader := bufio.NewReader(os.Stdin)
    if input, err := reader.ReadString('\n'); err != nil {
        fmt.Println(err)
        fmt.Println("-----------")
        fmt.Println(input)
        os.Exit(1)
    }
    fmt.Println("ESCAPED!")
    os.Exit(m.Run())
}

I have read in circles how to mock this for unit tests and the sort, but my case is more of a functional test runner. Is there a way, or even some trickery, that will allow me to open or change the test processes stdin?

Answer 1

You can redirect os.Stdin, it depends on OS though:

package tests

import (
    "fmt"
        "os"
        "testing"
    "bufio"
    "runtime"
)

func TestMain(m *testing.M) {

    var ttyName string
    if runtime.GOOS == "windows" {
        ttyName = "con"
    } else {
        ttyName = "/dev/tty"
    }   

    f, err := os.Open(ttyName)
    if err != nil {
        panic(err)
    }
    defer f.Close()

    oldStdin := os.Stdin
    defer func() { os.Stdin = oldStdin }()

    os.Stdin = f

    reader := bufio.NewReader(os.Stdin)
        if input, err := reader.ReadString('\n'); err != nil {
        fmt.Println("Error:", err)
        fmt.Println("-----------")
        fmt.Println(input)
        os.Exit(1)
    }
    fmt.Println("ESCAPED!")
    os.Exit(m.Run())
}

func TestHello(t *testing.T){
    fmt.Println("Hello")
}