diff --git a/replay/replay.go b/replay/replay.go
index 9ad37be..c6cf4f7 100644
--- a/replay/replay.go
+++ b/replay/replay.go
@@ -23,7 +23,7 @@ type AntiReplay struct {
 	// for inbound packets
 	mu     sync.Mutex
 	last   uint64
-	circle [1 << 7]uint64
+	circle [NumBlocks]uint64
 }
 
 func NewAntiReplay() *AntiReplay {
diff --git a/replay/replay_test.go b/replay/replay_test.go
new file mode 100644
index 0000000..0254d5c
--- /dev/null
+++ b/replay/replay_test.go
@@ -0,0 +1,77 @@
+package replay
+
+import (
+	"encoding/binary"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"math/rand"
+	"testing"
+)
+
+func TestAntiReplay_Verify(t *testing.T) {
+	t.Run("NoReplays", func(t *testing.T) {
+		// ASSIGN
+		r := NewAntiReplay()
+
+		start := rand.Uint64()
+		sum := make([]byte, 8)
+
+		// ACT + ASSERT
+		for i := start; i < start+128; i++ {
+			// ACT
+			binary.LittleEndian.PutUint64(sum, i)
+			err := r.Verify(nil, sum)
+
+			// ASSERT
+			require.Nil(t, err)
+		}
+	})
+
+	t.Run("ImmediateReplay", func(t *testing.T) {
+		// ASSIGN
+		r := NewAntiReplay()
+
+		start := rand.Uint64()
+		sum := make([]byte, 8)
+
+		// ACT
+		binary.LittleEndian.PutUint64(sum, start)
+
+		err1 := r.Verify(nil, sum)
+		err2 := r.Verify(nil, sum)
+
+		// ASSERT
+		require.Nil(t, err1)
+		require.Equal(t, ErrReplayedPacket, err2)
+	})
+
+	t.Run("RandomReplays", func(t *testing.T) {
+		// ASSIGN
+		r := NewAntiReplay()
+
+		start := rand.Uint64()
+		sum := make([]byte, 8)
+
+		random := make([]byte, 512/8)
+		rand.Read(random)
+
+		// ACT + ASSERT
+		for i := 0; i < 512; i++ {
+			// ACT
+			replay := (random[i/8] & (1 << (i % 8)) > 0) && i != 0
+			if !replay {
+				start++
+			}
+
+			binary.LittleEndian.PutUint64(sum, start)
+			err := r.Verify(nil, sum)
+
+			// ASSERT
+			if replay {
+				assert.Equal(t, ErrReplayedPacket, err)
+			} else {
+				assert.Nil(t, err)
+			}
+		}
+	})
+}