diff --git a/src/lib/exvar_test.go b/src/lib/exvar_test.go
new file mode 100644
index 0000000..2948fc6
--- /dev/null
+++ b/src/lib/exvar_test.go
@@ -0,0 +1,54 @@
+// 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 exvar
+
+import (
+	"exvar";
+	"fmt";
+	"testing";
+)
+
+func TestSimpleCounter(t *testing.T) {
+	// Unknown exvar should be zero, and return !ok.
+	x, ok := Get("requests");
+	if x != 0 || ok {
+		t.Errorf("Get(nonexistent) = (%v, %v), want (%v, %v)",
+		         x, ok, 0, false)
+	}
+
+	Increment("requests", 1);
+	Increment("requests", 3);
+	x, ok = Get("requests");
+	if x != 4 || !ok {
+		t.Errorf("Get('requests') = (%v, %v), want (%v, %v)",
+		         x, ok, 4, true)
+	}
+
+	out := String();
+	if out != "requests 4\n" {
+		t.Errorf("String() = \"%v\", want \"requests 4\n\"",
+		         out);
+	}
+}
+
+func hammer(name string, total int, done chan <- int) {
+	for i := 0; i < total; i++ {
+		Increment(name, 1)
+	}
+	done <- 1
+}
+
+func TestHammer(t *testing.T) {
+	Set("hammer-times", 0);
+	sync := make(chan int);
+	hammer_times := int(1e5);
+	go hammer("hammer-times", hammer_times, sync);
+	go hammer("hammer-times", hammer_times, sync);
+	<-sync;
+	<-sync;
+	if final, ok := Get("hammer-times"); final != 2 * hammer_times {
+		t.Errorf("hammer-times = %v, want %v", final, 2 * hammer_times)
+	}
+}