[#53] session: move XHeader from neofs-api-go

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

session/xheader_test.go

@@ -0,0 +1,58 @@
+package session
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neofs-api-go/v2/session"
+	"github.com/stretchr/testify/require"
+)
+
+func TestXHeader(t *testing.T) {
+	x := NewXHeader()
+
+	key := "some key"
+	val := "some value"
+
+	x.SetKey(key)
+	x.SetValue(val)
+
+	require.Equal(t, key, x.Key())
+	require.Equal(t, val, x.Value())
+
+	xV2 := x.ToV2()
+
+	require.Equal(t, key, xV2.GetKey())
+	require.Equal(t, val, xV2.GetValue())
+}
+
+func TestNewXHeaderFromV2(t *testing.T) {
+	t.Run("from nil", func(t *testing.T) {
+		var x *session.XHeader
+
+		require.Nil(t, NewXHeaderFromV2(x))
+	})
+}
+
+func TestXHeader_ToV2(t *testing.T) {
+	t.Run("nil", func(t *testing.T) {
+		var x *XHeader
+
+		require.Nil(t, x.ToV2())
+	})
+}
+
+func TestNewXHeader(t *testing.T) {
+	t.Run("default values", func(t *testing.T) {
+		xh := NewXHeader()
+
+		// check initial values
+		require.Empty(t, xh.Value())
+		require.Empty(t, xh.Key())
+
+		// convert to v2 message
+		xhV2 := xh.ToV2()
+
+		require.Empty(t, xhV2.GetValue())
+		require.Empty(t, xhV2.GetKey())
+	})
+}