Add timeutil test

Makefile

@@ -0,0 +1,2 @@
+test:
+	go test ./internal/timeutil

internal/timeutil/timeutil_test.go

@@ -0,0 +1,29 @@
+package timeutil
+
+import (
+	"testing"
+	"time"
+)
+
+func TestFormatDuration(t *testing.T) {
+	now := time.Now().Unix() * 1000
+	var tests = []struct {
+		input int64
+		want  string
+	}{
+		{now, "less than a minute"},
+		{now - 1.4*60*1000, "1 minute"},
+		{now - 1.5*60*1000, "2 minutes"},
+		{now - 44*60*1000, "44 minutes"},
+		{now - 2*60*60*1000, "about 2 hours"},
+		{now - 1439*60*1000, "about 24 hours"},
+		{now - 1440*60*1000, "1 day"},
+		{now - 3*43200*60*1000, "3 months"},
+		{now - 24*43200*60*1000, "about 2 years"},
+	}
+	for _, test := range tests {
+		if got := FormatDuration(test.input); got != test.want {
+			t.Errorf("FormatDuration(%d) = %q, want %q", test.input, got, test.want)
+		}
+	}
+}