add test for once

R=r
DELTA=31  (31 added, 0 deleted, 0 changed)
OCL=21043
CL=21175

src/lib/Makefile

@@ -37,6 +37,7 @@ FILES=\
 TEST=\
 	bignum\
 	bufio\
+	once\
 	sort\
 	strings\
 	utf8\

src/lib/once_test.go

+// Copyright 2009 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.
+
+package once
+
+import (
+	"once";
+	"testing";
+)
+
+var ncall int;
+func Call() {
+	ncall++
+}
+
+export func TestOnce(t *testing.T) {
+	ncall = 0;
+	once.Do(&Call);
+	if ncall != 1 {
+		t.Fatalf("once.Do(&Call) didn't Call(): ncall=%d", ncall);
+	}
+	once.Do(&Call);
+	if ncall != 1 {
+		t.Fatalf("second once.Do(&Call) did Call(): ncall=%d", ncall);
+	}
+	once.Do(&Call);
+	if ncall != 1 {
+		t.Fatalf("third once.Do(&Call) did Call(): ncall=%d", ncall);
+	}
+}