diff --git a/shaper_test.go b/shaper_test.go
new file mode 100644
index 0000000..6f6d265
--- /dev/null
+++ b/shaper_test.go
@@ -0,0 +1,30 @@
+package smux
+
+import (
+	"container/heap"
+	"testing"
+)
+
+func TestShaper(t *testing.T) {
+	w1 := writeRequest{prio: 10}
+	w2 := writeRequest{prio: 10}
+	w3 := writeRequest{prio: 20}
+	w4 := writeRequest{prio: 100}
+
+	var reqs shaperHeap
+	heap.Push(&reqs, w4)
+	heap.Push(&reqs, w3)
+	heap.Push(&reqs, w2)
+	heap.Push(&reqs, w1)
+
+	var lastPrio uint64
+	for len(reqs) > 0 {
+		w := heap.Pop(&reqs).(writeRequest)
+		if w.prio < lastPrio {
+			t.Fatal("incorrect shaper priority")
+		}
+
+		t.Log("prio:", w.prio)
+		lastPrio = w.prio
+	}
+}