time: give a helpful message when we can't set the time zone for testing.

Fixes #1625.

R=bradfitzgo, bradfitzwork, r2
CC=golang-dev
https://golang.org/cl/4295060

diff --git a/src/pkg/time/time_test.go b/src/pkg/time/time_test.go
index c86bca1b49875c823ed1a524e3e157256f77b64c..1d83291c097a8bd88bba1049218ed4db74c42fbe 100644 (file)
--- a/src/pkg/time/time_test.go
+++ b/src/pkg/time/time_test.go
@@ -19,6 +19,18 @@ func init() {
        os.Setenv("TZ", "America/Los_Angeles")
 }
 
+// We should be in PST/PDT, but if the time zone files are missing we
+// won't be. The purpose of this test is to at least explain why some of
+// the subsequent tests fail.
+func TestZoneData(t *testing.T) {
+       lt := LocalTime()
+       // PST is 8 hours west, PDT is 7 hours west.  We could use the name but it's not unique.
+       if off := lt.ZoneOffset; off != -8*60*60 && off != -7*60*60 {
+               t.Errorf("Unable to find US Pacific time zone data for testing; time zone is %q offset %d", lt.Zone, off)
+               t.Error("Likely problem: the time zone files have not been installed.")
+       }
+}
+
 type TimeTest struct {
        seconds int64
        golden  Time