Replace "ELVISH_TEST_TIME_SCALE" literals with a constant

pkg/testutil/scaled_ms.go

@@ -4,6 +4,8 @@ import (
 	"os"
 	"strconv"
 	"time"
+
+	"github.com/elves/elvish/pkg/util"
 )
 
 // ScaledMs returns ms milliseconds, scaled by the ELVISH_TEST_TIME_SCALE
@@ -15,7 +17,7 @@ func ScaledMs(ms int) time.Duration {
 }
 
 func getTestTimeScale() float64 {
-	env := os.Getenv("ELVISH_TEST_TIME_SCALE")
+	env := os.Getenv(util.EnvELVISH_TEST_TIME_SCALE)
 	if env == "" {
 		return 1
 	}

pkg/testutil/scaled_ms_test.go

@@ -4,6 +4,8 @@ import (
 	"os"
 	"testing"
 	"time"
+
+	"github.com/elves/elvish/pkg/util"
 )
 
 var scaledMsTests = []struct {
@@ -25,12 +27,12 @@ var scaledMsTests = []struct {
 }
 
 func TestScaledMs(t *testing.T) {
-	envSave := os.Getenv("ELVISH_TEST_TIME_SCALE")
-	defer os.Setenv("ELVISH_TEST_TIME_SCALE", envSave)
+	envSave := os.Getenv(util.EnvELVISH_TEST_TIME_SCALE)
+	defer os.Setenv(util.EnvELVISH_TEST_TIME_SCALE, envSave)
 
 	for _, test := range scaledMsTests {
 		t.Run(test.name, func(t *testing.T) {
-			os.Setenv("ELVISH_TEST_TIME_SCALE", test.env)
+			os.Setenv(util.EnvELVISH_TEST_TIME_SCALE, test.env)
 			got := ScaledMs(test.ms)
 			if got != test.want {
 				t.Errorf("got %v, want %v", got, test.want)

pkg/util/util.go

@@ -6,11 +6,12 @@ package util
 // Note that some of these env vars may be significant only in special
 // circumstances; such as when running unit tests.
 const (
-	EnvHOME            = "HOME"
-	EnvPATH            = "PATH"
-	EnvPATHEXT         = "PATHEXT"
-	EnvPWD             = "PWD"
-	EnvSHLVL           = "SHLVL"
-	EnvLS_COLORS       = "LS_COLORS"
-	EnvXDG_RUNTIME_DIR = "XDG_RUNTIME_DIR"
+	EnvHOME                   = "HOME"
+	EnvPATH                   = "PATH"
+	EnvPATHEXT                = "PATHEXT"
+	EnvPWD                    = "PWD"
+	EnvSHLVL                  = "SHLVL"
+	EnvLS_COLORS              = "LS_COLORS"
+	EnvXDG_RUNTIME_DIR        = "XDG_RUNTIME_DIR"
+	EnvELVISH_TEST_TIME_SCALE = "ELVISH_TEST_TIME_SCALE"
 )