Refactor spawn-daemon so it can be used by all OSes and make it write exit code to a file

command/spawn_daemon_test.go

@@ -0,0 +1,48 @@
+package command
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os/exec"
+	"testing"
+)
+
+type nopCloser struct {
+	io.ReadWriter
+}
+
+func (n *nopCloser) Close() error {
+	return nil
+}
+
+func TestSpawnDaemon_WriteExitStatus(t *testing.T) {
+	// Check if there is python.
+	path, err := exec.LookPath("python")
+	if err != nil {
+		t.Skip("python not detected")
+	}
+
+	var b bytes.Buffer
+	daemon := &SpawnDaemonCommand{exitFile: &nopCloser{&b}}
+
+	code := 3
+	cmd := exec.Command(path, "./test-resources/exiter.py", fmt.Sprintf("%d", code))
+	err = cmd.Run()
+	actual := daemon.writeExitStatus(err)
+	if actual != code {
+		t.Fatalf("writeExitStatus(%v) returned %v; want %v", err, actual, code)
+	}
+
+	// De-serialize the passed command.
+	var exitStatus SpawnExitStatus
+	dec := json.NewDecoder(&b)
+	if err := dec.Decode(&exitStatus); err != nil {
+		t.Fatalf("failed to decode exit status: %v", err)
+	}
+
+	if exitStatus.ExitCode != code {
+		t.Fatalf("writeExitStatus(%v) wrote exit status %v; want %v", err, exitStatus.ExitCode, code)
+	}
+}