diff --git a/fetcher.go b/fetcher.go
index 44812bd..0e898f1 100644
--- a/fetcher.go
+++ b/fetcher.go
@@ -1,7 +1,6 @@
 package cache
 
 import (
-	"errors"
 	"fmt"
 )
 
@@ -33,7 +32,7 @@ func (f *fetcher) Register(keyPrefix string, cbf callbackFunc) bool {
 
 func (f *fetcher) Execute(key string) (interface{}, error) {
 	if len(key) < f.prefixLen {
-		return nil, errors.New("Invalid Key " + key)
+		return nil, fmt.Errorf(errInvalidKey, key)
 	}
 	keyPrefix := key[:f.prefixLen]
 	cbf, ok := f.cb[keyPrefix]
diff --git a/fetcher_test.go b/fetcher_test.go
index 55af0bd..81a7ae3 100644
--- a/fetcher_test.go
+++ b/fetcher_test.go
@@ -5,6 +5,63 @@ import (
 	"testing"
 )
 
+func Test_fetcher_Register(t *testing.T) {
+	type fields struct {
+		cb        map[string]callbackFunc
+		prefixLen int
+	}
+	type args struct {
+		keyPrefix string
+		cbf       callbackFunc
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   bool
+	}{
+		// TODO: Add test cases.
+		{
+			name:   "Registering Invalid KeyPrefix",
+			fields: fields(*NewFetcher(5)),
+			args: args{
+				keyPrefix: "AAG0022222",
+				cbf:       nil,
+			},
+			want: false,
+		},
+		{
+			name:   "Registering Empty KeyPrefix",
+			fields: fields(*NewFetcher(5)),
+			args: args{
+				keyPrefix: "",
+				cbf:       nil,
+			},
+			want: false,
+		},
+		{
+			name:   "Registration Valid KeyPrefix",
+			fields: fields(*NewFetcher(5)),
+			args: args{
+				keyPrefix: "AAG00",
+				cbf:       CbGetAdUnitConfig,
+			},
+			want: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			f := &fetcher{
+				cb:        tt.fields.cb,
+				prefixLen: tt.fields.prefixLen,
+			}
+			if got := f.Register(tt.args.keyPrefix, tt.args.cbf); got != tt.want {
+				t.Errorf("fetcher.Register() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
 func Test_fetcher_Execute(t *testing.T) {
 	type fields struct {
 		cb        map[string]callbackFunc
@@ -54,15 +111,17 @@ func Test_fetcher_Execute(t *testing.T) {
 		{
 			name: "Valid Key Execution",
 			fields: fields{
-				cb:        make(map[string]callbackFunc),
+				cb: map[string]callbackFunc{
+					"AAG00": CbGetAdUnitConfig,
+					"AAA00": nil,
+					"AAB00": nil,
+				},
 				prefixLen: 5,
 			},
 			args: args{
 				key: "AAG00_5890",
 			},
-			want: f.cb{
-				"afewv",
-			},
+			want:    "AdUnitConfig",
 			wantErr: false,
 		},
 	}
@@ -74,10 +133,7 @@ func Test_fetcher_Execute(t *testing.T) {
 				prefixLen: tt.fields.prefixLen,
 			}
 			got, err := f.Execute(tt.args.key)
-			// if errors.Is(err, tt.wantErr) {
-			// 	t.Errorf("fetcher.Execute() error = %v, wantErr %v", err, tt.wantErr)
-			// 	return
-			// }
+
 			if (err != nil) != tt.wantErr {
 				t.Errorf("fetcher.Execute() error = %v, wantErr %v", err, tt.wantErr)
 				return
@@ -88,3 +144,16 @@ func Test_fetcher_Execute(t *testing.T) {
 		})
 	}
 }
+
+func CbGetAdUnitConfig(key string) (interface{}, error) {
+	//Spliting Key to Call Respective DB call
+	//info := strings.Split(key, "_")
+
+	//profileID, _ := strconv.Atoi(info[1])
+	//displayVersionID, _ := strconv.Atoi(info[2])
+
+	data := "AdUnitConfig"
+
+	return data, nil
+
+}