Hermetic Executable Helper Testing via Environment Flag Subprocess Forking

package main
 
import (
	"os"
	"os/exec"
	"testing"
)
 
func HelperProcess(t *testing.T) {
	if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" {
		return
	}
	os.Stdout.WriteString("simulated subprocess output")
	os.Exit(0)
}
 
func TestSubprocessExecution(t *testing.T) {
	cmd := exec.Command(os.Args[0], "-test.run=HelperProcess")
	cmd.Env = append(os.Environ(), "GO_WANT_HELPER_PROCESS=1")
	out, err := cmd.Output()
	if err != nil || string(out) != "simulated subprocess output" {
		t.Fatalf("Subprocess testing failed, output: %s", string(out))
	}
}