Adding UTs part-1

Change-Id: I7fdb7751f536d1a616cf2a81b7ef16747d71f692
diff --git a/voltha-go-controller/onos_nbi/oltflowservice_test.go b/voltha-go-controller/onos_nbi/oltflowservice_test.go
new file mode 100644
index 0000000..6b78cc9
--- /dev/null
+++ b/voltha-go-controller/onos_nbi/oltflowservice_test.go
@@ -0,0 +1,56 @@
+/*
+* Copyright 2023-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 onosnbi
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestOltFlowServiceHandle_ServeHTTP(t *testing.T) {
+	req, err := http.NewRequest("GET", "/serve_http/", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	rr := httptest.NewRecorder()
+
+	type args struct {
+		w http.ResponseWriter
+		r *http.Request
+	}
+	tests := []struct {
+		name string
+		oh   *OltFlowServiceHandle
+		args args
+	}{
+		{
+			name: "OltFlowServiceHandle_ServeHTTP",
+			args: args{
+				w: rr,
+				r: req,
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			oh := &OltFlowServiceHandle{}
+			oh.ServeHTTP(tt.args.w, tt.args.r)
+		})
+	}
+}