[#85] Fix get latest version node

Signed-off-by: Roman Loginov <r.loginov@yadro.com>

tree/tree_test.go

@@ -0,0 +1,143 @@
+package tree
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+type nodeMeta struct {
+	key   string
+	value []byte
+}
+
+func (m nodeMeta) GetKey() string {
+	return m.key
+}
+
+func (m nodeMeta) GetValue() []byte {
+	return m.value
+}
+
+type nodeResponse struct {
+	meta      []nodeMeta
+	timestamp uint64
+}
+
+func (n nodeResponse) GetTimestamp() uint64 {
+	return n.timestamp
+}
+
+func (n nodeResponse) GetMeta() []Meta {
+	res := make([]Meta, len(n.meta))
+	for i, value := range n.meta {
+		res[i] = value
+	}
+	return res
+}
+
+func TestGetLatestNode(t *testing.T) {
+	for _, tc := range []struct {
+		name        string
+		nodes       []NodeResponse
+		exceptedOID string
+		error       bool
+	}{
+		{
+			name:  "empty",
+			nodes: []NodeResponse{},
+			error: true,
+		},
+		{
+			name: "one node of the object version",
+			nodes: []NodeResponse{
+				nodeResponse{
+					timestamp: 1,
+					meta: []nodeMeta{
+						{
+							key:   oidKV,
+							value: []byte("oid1"),
+						},
+					},
+				},
+			},
+			exceptedOID: "oid1",
+		},
+		{
+			name: "one node of the object version and one node of the secondary object",
+			nodes: []NodeResponse{
+				nodeResponse{
+					timestamp: 3,
+					meta:      []nodeMeta{},
+				},
+				nodeResponse{
+					timestamp: 1,
+					meta: []nodeMeta{
+						{
+							key:   oidKV,
+							value: []byte("oid1"),
+						},
+					},
+				},
+			},
+			exceptedOID: "oid1",
+		},
+		{
+			name: "all nodes represent a secondary object",
+			nodes: []NodeResponse{
+				nodeResponse{
+					timestamp: 3,
+					meta:      []nodeMeta{},
+				},
+				nodeResponse{
+					timestamp: 5,
+					meta:      []nodeMeta{},
+				},
+			},
+			error: true,
+		},
+		{
+			name: "several nodes of different types and with different timestamp",
+			nodes: []NodeResponse{
+				nodeResponse{
+					timestamp: 1,
+					meta: []nodeMeta{
+						{
+							key:   oidKV,
+							value: []byte("oid1"),
+						},
+					},
+				},
+				nodeResponse{
+					timestamp: 3,
+					meta:      []nodeMeta{},
+				},
+				nodeResponse{
+					timestamp: 4,
+					meta: []nodeMeta{
+						{
+							key:   oidKV,
+							value: []byte("oid2"),
+						},
+					},
+				},
+				nodeResponse{
+					timestamp: 6,
+					meta:      []nodeMeta{},
+				},
+			},
+			exceptedOID: "oid2",
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			actualNode, err := getLatestNode(tc.nodes)
+			if tc.error {
+				require.Error(t, err)
+				return
+			}
+
+			require.NoError(t, err)
+			require.Equal(t, tc.exceptedOID, string(actualNode.GetMeta()[0].GetValue()))
+		})
+	}
+}