1 files changed, 90 insertions, 0 deletions
diff --git a/src/time/zoneinfo_unix_test.go b/src/time/zoneinfo_unix_test.go
new file mode 100644
index 0000000..92680c4
--- /dev/null
+++ b/src/time/zoneinfo_unix_test.go
@@ -0,0 +1,90 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build unix && !ios && !android
+
+package time_test
+
+import (
+	"os"
+	"testing"
+	"time"
+)
+
+func TestEnvTZUsage(t *testing.T) {
+	const env = "TZ"
+	tz, ok := os.LookupEnv(env)
+	if !ok {
+		defer os.Unsetenv(env)
+	} else {
+		defer os.Setenv(env, tz)
+	}
+	defer time.ForceUSPacificForTesting()
+
+	localZoneName := "Local"
+	// The file may not exist.
+	if _, err := os.Stat("/etc/localtime"); os.IsNotExist(err) {
+		localZoneName = "UTC"
+	}
+
+	cases := []struct {
+		nilFlag bool
+		tz      string
+		local   string
+	}{
+		// no $TZ means use the system default /etc/localtime.
+		{true, "", localZoneName},
+		// $TZ="" means use UTC.
+		{false, "", "UTC"},
+		{false, ":", "UTC"},
+		{false, "Asia/Shanghai", "Asia/Shanghai"},
+		{false, ":Asia/Shanghai", "Asia/Shanghai"},
+		{false, "/etc/localtime", localZoneName},
+		{false, ":/etc/localtime", localZoneName},
+	}
+
+	for _, c := range cases {
+		time.ResetLocalOnceForTest()
+		if c.nilFlag {
+			os.Unsetenv(env)
+		} else {
+			os.Setenv(env, c.tz)
+		}
+		if time.Local.String() != c.local {
+			t.Errorf("invalid Local location name for %q: got %q want %q", c.tz, time.Local, c.local)
+		}
+	}
+
+	time.ResetLocalOnceForTest()
+	// The file may not exist on Solaris 2 and IRIX 6.
+	path := "/usr/share/zoneinfo/Asia/Shanghai"
+	os.Setenv(env, path)
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		if time.Local.String() != "UTC" {
+			t.Errorf(`invalid path should fallback to UTC: got %q want "UTC"`, time.Local)
+		}
+		return
+	}
+	if time.Local.String() != path {
+		t.Errorf(`custom path should lead to path itself: got %q want %q`, time.Local, path)
+	}
+
+	timeInUTC := time.Date(2009, 1, 1, 12, 0, 0, 0, time.UTC)
+	sameTimeInShanghai := time.Date(2009, 1, 1, 20, 0, 0, 0, time.Local)
+	if !timeInUTC.Equal(sameTimeInShanghai) {
+		t.Errorf("invalid timezone: got %q want %q", timeInUTC, sameTimeInShanghai)
+	}
+
+	time.ResetLocalOnceForTest()
+	os.Setenv(env, ":"+path)
+	if time.Local.String() != path {
+		t.Errorf(`custom path should lead to path itself: got %q want %q`, time.Local, path)
+	}
+
+	time.ResetLocalOnceForTest()
+	os.Setenv(env, path[:len(path)-1])
+	if time.Local.String() != "UTC" {
+		t.Errorf(`invalid path should fallback to UTC: got %q want "UTC"`, time.Local)
+	}
+}