From 86769d453507574ff3e8c9faa4e995e104e32f5b Mon Sep 17 00:00:00 2001
From: c9s <yoan@maicoin.com>
Date: Tue, 18 Aug 2020 13:14:52 +0800
Subject: [PATCH] add kline window tail test

---
 bbgo/types/kline.go      |  9 +++++++--
 bbgo/types/kline_test.go | 22 ++++++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 bbgo/types/kline_test.go

diff --git a/bbgo/types/kline.go b/bbgo/types/kline.go
index 570328fe9..1af945f5b 100644
--- a/bbgo/types/kline.go
+++ b/bbgo/types/kline.go
@@ -320,9 +320,14 @@ func (k KLineWindow) Take(size int) KLineWindow {
 
 func (k KLineWindow) Tail(size int) KLineWindow {
 	if len(k) <= size {
-		return k[:]
+		win := make(KLineWindow, len(k))
+		copy(win, k)
+		return win
 	}
-	return k[len(k)-size:]
+
+	win := make(KLineWindow, size)
+	copy(win, k[len(k)-size:])
+	return win
 }
 
 func (k *KLineWindow) Truncate(size int) {
diff --git a/bbgo/types/kline_test.go b/bbgo/types/kline_test.go
new file mode 100644
index 000000000..b550d560b
--- /dev/null
+++ b/bbgo/types/kline_test.go
@@ -0,0 +1,22 @@
+package types
+
+import ("testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestKLineWindow_Tail(t *testing.T) {
+	var win = KLineWindow{
+		{ Open: "11600.0", Close: "11600.0", High: "11600.0", Low: "11600.0"},
+		{ Open: "11600.0", Close: "11600.0", High: "11600.0", Low: "11600.0"},
+	}
+
+	var win2 = win.Tail(1)
+	assert.Len(t, win2, 1)
+
+	var win3 = win.Tail(2)
+	assert.Len(t, win3, 2)
+
+	var win4 = win.Tail(3)
+	assert.Len(t, win4, 2)
+}