add unit test for isWsl

internal/login/login.go

@@ -232,35 +232,37 @@ func generateState() (string, error) {
 }
 
 // check for Windows Subsystem for Linux
-func isWsl() bool {
+func isWsl(sc util.Syscall) bool {
 	// the common factor between WSL distros is the Microsoft-specific kernel version, so we check for that
 	// SUSE, WSLv1: 4.4.0-19041-Microsoft
 	// Ubuntu, WSLv2: 4.19.128-microsoft-standard
+	const wslIdentifier = "microsoft"
 	var uname syscall.Utsname
-	if err := syscall.Uname(&uname); err == nil {
+	if err := sc.Uname(&uname); err == nil {
 		var kernel []byte
 		for _, b := range uname.Release {
 			if b == 0 {
 				break
 			}
 			kernel = append(kernel, byte(b))
 		}
-		return strings.Contains(strings.ToLower(string(kernel)), "microsoft")
+		return strings.Contains(strings.ToLower(string(kernel)), wslIdentifier)
 	}
 	return false
 }
 
 func openBrowser(url string) error {
+	const rundllParameters = "url.dll,FileProtocolHandler"
 	var err error
 	switch runtime.GOOS {
 	case "linux":
-		if isWsl() {
-			err = exec.Command("rundll32.exe", "url.dll,FileProtocolHandler", url).Start()
+		if isWsl(util.DefaultSyscall) {
+			err = exec.Command("rundll32.exe", rundllParameters, url).Start()
 		} else {
 			err = exec.Command("xdg-open", url).Start()
 		}
 	case "windows":
-		err = exec.Command("rundll32", "url.dll,FileProtocolHandler", url).Start()
+		err = exec.Command("rundll32", rundllParameters, url).Start()
 	case "darwin":
 		err = exec.Command("open", url).Start()
 	default:

internal/login/login_test.go

@@ -4,13 +4,16 @@ package login
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"syscall"
 	"testing"
 	"time"
 
 	"github.com/spf13/viper"
+	"github.com/stretchr/testify/assert"
 	"github.com/twitchdev/twitch-cli/internal/util"
 )
 
@@ -157,3 +160,35 @@ func TestUserAuthServer(t *testing.T) {
 	a.Equal(state, ur.State, "State mismatch")
 	a.Equal(code, ur.Code, "Code mismatch")
 }
+
+func TestIsWsl(t *testing.T) {
+	a := assert.New(t)
+
+	var (
+		ubuntu20Wsl2 = [65]int8{52, 46, 49, 57, 46, 49, 50, 56, 45, 109, 105, 99, 114, 111, 115, 111, 102, 116, 45, 115, 116, 97, 110, 100, 97, 114, 100, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+		archReal     = [65]int8{53, 46, 49, 49, 46, 49, 49, 45, 97, 114, 99, 104, 49, 45, 49, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+	)
+
+	result := isWsl(util.Syscall{
+		Uname: func(buf *syscall.Utsname) (err error) {
+			buf.Release = ubuntu20Wsl2
+			return nil
+		},
+	})
+	a.True(result)
+
+	result = isWsl(util.Syscall{
+		Uname: func(buf *syscall.Utsname) (err error) {
+			buf.Release = archReal
+			return nil
+		},
+	})
+	a.False(result)
+
+	result = isWsl(util.Syscall{
+		Uname: func(buf *syscall.Utsname) (err error) {
+			return errors.New("mocked error")
+		},
+	})
+	a.False(result)
+}

internal/util/syscall.go

@@ -0,0 +1,12 @@
+package util
+
+import "syscall"
+
+// Syscall wraps syscalls used in the application for unit testing purposes
+type Syscall struct {
+	Uname func(buf *syscall.Utsname) (err error)
+}
+
+var DefaultSyscall = Syscall{
+	Uname: syscall.Uname,
+}