diff --git a/pkg/types/sliceorderbook_test.go b/pkg/types/sliceorderbook_test.go
new file mode 100644
index 000000000..06aedd3ae
--- /dev/null
+++ b/pkg/types/sliceorderbook_test.go
@@ -0,0 +1,27 @@
+package types
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSliceOrderBook_CopyDepth(t *testing.T) {
+	b := &SliceOrderBook{
+		Bids: PriceVolumeSlice{
+			{Price: number(0.119), Volume: number(100.0)},
+			{Price: number(0.118), Volume: number(100.0)},
+			{Price: number(0.117), Volume: number(100.0)},
+			{Price: number(0.116), Volume: number(100.0)},
+		},
+		Asks: PriceVolumeSlice{
+			{Price: number(0.120), Volume: number(100.0)},
+			{Price: number(0.121), Volume: number(100.0)},
+			{Price: number(0.122), Volume: number(100.0)},
+		},
+	}
+
+	copied := b.CopyDepth(0)
+	assert.Equal(t, 3, len(copied.SideBook(SideTypeSell)))
+	assert.Equal(t, 4, len(copied.SideBook(SideTypeBuy)))
+}