diff --git a/internal/pkg/core/statsmanager_test.go b/internal/pkg/core/statsmanager_test.go
new file mode 100644
index 0000000..6ea2487
--- /dev/null
+++ b/internal/pkg/core/statsmanager_test.go
@@ -0,0 +1,283 @@
+/*
+ * Copyright 2019-present Open Networking Foundation
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//Package core provides the utility for olt devices, flows and statistics
+package core
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/opencord/voltha-lib-go/v3/pkg/log"
+	"github.com/opencord/voltha-protos/v3/go/openolt"
+	"github.com/opencord/voltha-protos/v3/go/voltha"
+)
+
+func init() {
+	_, _ = log.AddPackage(log.JSON, log.DebugLevel, nil)
+}
+func TestOpenOltStatisticsMgr_PortStatisticsIndication(t *testing.T) {
+	device := &voltha.Device{
+		Id:       "olt",
+		Root:     true,
+		ParentId: "logical_device",
+		Ports: []*voltha.Port{
+			{PortNo: 1, Label: "pon", Type: voltha.Port_ETHERNET_UNI},
+			{PortNo: 2, Label: "nni", Type: voltha.Port_ETHERNET_NNI},
+		},
+		ProxyAddress: &voltha.Device_ProxyAddress{
+			DeviceId:       "olt",
+			DeviceType:     "onu",
+			ChannelId:      1,
+			ChannelGroupId: 1,
+		},
+		ConnectStatus: 1,
+	}
+	dh := newMockDeviceHandler()
+	dh.device = device
+	StatMgr := NewOpenOltStatsMgr(dh)
+
+	type args struct {
+		PortStats *openolt.PortStatistics
+	}
+	tests := []struct {
+		name string
+		args args
+	}{
+		// TODO: Add test cases.
+		{"PortStatisticsIndication", args{PortStats: &openolt.PortStatistics{}}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+
+			StatMgr.PortStatisticsIndication(tt.args.PortStats, 16)
+		})
+	}
+}
+
+func TestOpenOltStatisticsMgr_publishMetrics(t *testing.T) {
+	type fields struct {
+		Device         *DeviceHandler
+		NorthBoundPort map[uint32]*NniPort
+		SouthBoundPort map[uint32]*PonPort
+	}
+	type args struct {
+		portType string
+		val      map[string]float32
+		portnum  uint32
+		context  map[string]string
+	}
+	ctx := map[string]string{}
+	ctx["deviceID"] = "Test"
+	ponmap := map[uint32]*PonPort{}
+	ponmap[0] = &PonPort{
+		PONID:          0,
+		DeviceID:       "onu1",
+		IntfID:         0,
+		PortNum:        0,
+		PortID:         0,
+		Label:          "",
+		ONUs:           nil,
+		ONUsByID:       nil,
+		RxBytes:        0,
+		RxPackets:      0,
+		RxUcastPackets: 0,
+		RxMcastPackets: 0,
+		RxBcastPackets: 0,
+		RxErrorPackets: 0,
+		TxBytes:        0,
+		TxPackets:      0,
+		TxUcastPackets: 0,
+		TxMcastPackets: 0,
+		TxBcastPackets: 0,
+		TxErrorPackets: 0,
+		RxCrcErrors:    0,
+		BipErrors:      0,
+	}
+	nnimap := map[uint32]*NniPort{}
+	nnimap[0] = &NniPort{
+		PortNum:        0,
+		Name:           "olt1",
+		LogicalPort:    0,
+		IntfID:         0,
+		RxBytes:        0,
+		RxPackets:      0,
+		RxUcastPackets: 0,
+		RxMcastPackets: uint64(1111),
+		RxBcastPackets: 0,
+		RxErrorPackets: 0,
+		TxBytes:        0,
+		TxPackets:      0,
+		TxUcastPackets: 0,
+		TxMcastPackets: 0,
+		TxBcastPackets: 0,
+		TxErrorPackets: 0,
+		RxCrcErrors:    0,
+		BipErrors:      0,
+	}
+	pval := make(map[string]float32)
+	pval["rx_bytes"] = float32(111)
+	nval := make(map[string]float32)
+	nval["rx_bytes"] = float32(111)
+	dhandlerNNI := newMockDeviceHandler()
+	dhandlerNNI.portStats = &OpenOltStatisticsMgr{Device: nil, SouthBoundPort: nil, NorthBoundPort: nnimap}
+	dhandlerPON := newMockDeviceHandler()
+	dhandlerPON.portStats = &OpenOltStatisticsMgr{Device: nil, SouthBoundPort: ponmap, NorthBoundPort: nil}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+	}{
+		{
+			name: "PublishNNIMetrics-1",
+			fields: fields{
+				Device:         dhandlerNNI,
+				NorthBoundPort: nnimap,
+				SouthBoundPort: nil,
+			},
+			args: args{
+				portType: "NNIStats",
+				val:      nval,
+				portnum:  0,
+				context:  ctx,
+			},
+		},
+		{
+			name: "PublishPONMetrics-1",
+			fields: fields{
+				Device:         dhandlerPON,
+				NorthBoundPort: nil,
+				SouthBoundPort: ponmap,
+			},
+			args: args{
+				portType: "PONStats",
+				val:      pval,
+				portnum:  0,
+				context:  ctx,
+			},
+		},
+		// TODO: Add test cases.
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			StatMgr := &OpenOltStatisticsMgr{
+				Device:         tt.fields.Device,
+				NorthBoundPort: tt.fields.NorthBoundPort,
+				SouthBoundPort: tt.fields.SouthBoundPort,
+			}
+			StatMgr.publishMetrics(tt.args.portType, tt.args.val, tt.args.portnum, tt.args.context, "onu1")
+
+		})
+	}
+}
+
+func TestOpenOltStatisticsMgr_collectNNIMetrics(t *testing.T) {
+	type fields struct {
+		Device         *DeviceHandler
+		NorthBoundPort map[uint32]*NniPort
+		SouthBoundPort map[uint32]*PonPort
+	}
+	type args struct {
+		nniID uint32
+	}
+	dhandler := newMockDeviceHandler()
+	pmconfig := make(map[string]*voltha.PmConfig)
+	pmconfig["rx_bytes"] = &voltha.PmConfig{Name: "olt"}
+
+	var res map[string]float32
+	nnimap := map[uint32]*NniPort{}
+	nnimap[0] = &NniPort{Name: "olt"}
+	nnimap[1] = &NniPort{Name: "olt"}
+	dh := &DeviceHandler{portStats: &OpenOltStatisticsMgr{Device: dhandler, SouthBoundPort: nil, NorthBoundPort: nnimap}}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   map[string]float32
+	}{
+		{"CollectNNIMetrics-1", fields{
+			Device:         dh,
+			NorthBoundPort: nnimap,
+			SouthBoundPort: nil,
+		}, args{0}, res},
+		{"CollectNNIMetrics-2", fields{
+			Device:         dh,
+			NorthBoundPort: nnimap,
+			SouthBoundPort: nil,
+		}, args{1}, res},
+		// TODO: Add test cases.
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			StatMgr := &OpenOltStatisticsMgr{
+				Device:         tt.fields.Device,
+				NorthBoundPort: tt.fields.NorthBoundPort,
+				SouthBoundPort: tt.fields.SouthBoundPort,
+			}
+			got := StatMgr.collectNNIMetrics(tt.args.nniID)
+			if reflect.TypeOf(got) != reflect.TypeOf(tt.want) {
+				t.Errorf("collectNNIMetrics() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestOpenOltStatisticsMgr_collectPONMetrics(t *testing.T) {
+	type fields struct {
+		Device         *DeviceHandler
+		NorthBoundPort map[uint32]*NniPort
+		SouthBoundPort map[uint32]*PonPort
+	}
+	type args struct {
+		pID uint32
+	}
+	dhandler := newMockDeviceHandler()
+	pmconfig := make(map[string]*voltha.PmConfig)
+	pmconfig["rx_bytes"] = &voltha.PmConfig{Name: "olt"}
+
+	var res map[string]float32
+	ponmap := map[uint32]*PonPort{}
+	ponmap[0] = &PonPort{DeviceID: "olt"}
+	ponmap[1] = &PonPort{DeviceID: "olt"}
+	dh := &DeviceHandler{portStats: &OpenOltStatisticsMgr{Device: dhandler, SouthBoundPort: ponmap, NorthBoundPort: nil}}
+
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   map[string]float32
+	}{
+		{"CollectPONMetrics-1", fields{
+			Device:         dh,
+			NorthBoundPort: nil,
+			SouthBoundPort: ponmap,
+		}, args{0}, res},
+		// TODO: Add test cases.
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			StatMgr := &OpenOltStatisticsMgr{
+				Device:         tt.fields.Device,
+				NorthBoundPort: tt.fields.NorthBoundPort,
+				SouthBoundPort: tt.fields.SouthBoundPort,
+			}
+			got := StatMgr.collectPONMetrics(tt.args.pID)
+			if reflect.TypeOf(got) != reflect.TypeOf(tt.want) {
+				t.Errorf("collectPONMetrics() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}