diff --git a/sync/monitor_test.go b/sync/monitor_test.go
new file mode 100644
index 0000000..a7b3eb5
--- /dev/null
+++ b/sync/monitor_test.go
@@ -0,0 +1,47 @@
+package usync
+
+import "testing"
+import "math/rand"
+
+func TestMonitor (test *testing.T) {
+	mon := NewMonitor(9)
+	func () {
+		value, done := mon.Borrow()
+		defer done()
+		test.Log(value)
+		if value != 9 { test.Fatal("not equal") }
+	} ()
+	func () {
+		value, done := mon.BorrowReturn()
+		value += 3
+		defer done(value)
+	} ()
+	func () {
+		value, done := mon.Borrow()
+		defer done()
+		test.Log(value)
+		if value != 12 { test.Fatal("not equal") }
+	} ()
+	mon.Set(11)
+	func () {
+		value, done := mon.Borrow()
+		defer done()
+		test.Log(value)
+		if value != 11 { test.Fatal("not equal") }
+	} ()
+}
+
+func TestMonitorConcurrent (test *testing.T) {
+	mon := NewMonitor(map[int] int { })
+	for index := 0; index < 16; index ++ {
+		go func () {
+			for index := 0; index < 8192; index ++ {
+				func () {
+					value, done := mon.Borrow()
+					defer done()
+					value[rand.Int()] = rand.Int()
+				} ()
+			}
+		} ()
+	}
+}