diff --git a/stack/stack.go b/stack/stack.go
index 1972a3c..df7c57b 100644
--- a/stack/stack.go
+++ b/stack/stack.go
@@ -33,6 +33,7 @@ func (as *Stack) Size() int {
 	return as.size
 }
 
+// String 从左到右 左边第一个表示Top 如链表 a(top)->b->c
 func (as *Stack) String() string {
 	content := ""
 	cur := as.top
@@ -50,6 +51,11 @@ func (as *Stack) String() string {
 }
 
 func (as *Stack) Values() []interface{} {
+
+	if as.size == 0 {
+		return nil
+	}
+
 	result := make([]interface{}, as.size, as.size)
 
 	cur := as.top
diff --git a/stack/stack_test.go b/stack/stack_test.go
index 6571ffa..66e43ef 100644
--- a/stack/stack_test.go
+++ b/stack/stack_test.go
@@ -1,5 +1,104 @@
 package lastack
 
+import "testing"
+
+func TestBase(t *testing.T) {
+	s := New()
+	if !s.Empty() {
+		t.Error("stack not empty")
+	}
+
+	if s.Size() != 0 {
+		t.Error("size != 0")
+	}
+
+	if s.Values() != nil {
+		t.Error(s.Values())
+	}
+}
+
+func TestPush(t *testing.T) {
+	s := New()
+
+	for i := 0; i < 5; i++ {
+		s.Push(i)
+	}
+
+	if s.Empty() {
+		t.Error("stack is empty")
+	}
+
+	if s.Size() == 0 {
+		t.Error("size == 0")
+	}
+
+	if s.Values() == nil {
+		t.Error("Values() != nil")
+	}
+
+	if s.String() != "4 3 2 1 0" {
+		t.Error(s.String())
+	}
+
+	if v, ok := s.Peek(); ok {
+		if v != 4 {
+			t.Error("why top != 4")
+		}
+	} else {
+		t.Error("not ok")
+	}
+
+	if v, ok := s.Pop(); ok {
+		if v != 4 {
+			t.Error("why top != 4")
+		}
+	} else {
+		t.Error("not ok")
+	}
+
+	if s.Size() != 4 {
+		t.Error("pop a element, size: 5 - 1 = 4")
+	}
+
+	//
+	if v, ok := s.Pop(); ok {
+		if v != 3 {
+			t.Error("why top != 3")
+		}
+	} else {
+		t.Error("not ok")
+	}
+
+	if s.Size() != 3 {
+		t.Error("pop a element, size: 4 - 1 = 3")
+	}
+
+	for _, ok := s.Pop(); ok != false; _, ok = s.Pop() {
+
+	}
+
+	if !s.Empty() && s.Size() != 0 {
+		t.Error("pop all, stack should be empty")
+	}
+
+	for i := 0; i < 5; i++ {
+		s.Push(i)
+	}
+
+	if s.Size() != 5 {
+		t.Error("size != 5")
+	}
+
+	s.Clear()
+	if !s.Empty() && s.Size() != 0 {
+		t.Error("pop all, stack should be empty")
+	}
+
+	if v, ok := s.Peek(); v != nil || ok != false {
+		t.Error("should be v == nil and ok == false")
+	}
+}
+
 // func BenchmarkPush(b *testing.B) {
 // 	s := New()
 // 	b.N = 200000