diff --git a/pkg/zonemgr/zone_file_cache_test.go b/pkg/zonemgr/zone_file_cache_test.go
index 6fc9f0a..a509db1 100644
--- a/pkg/zonemgr/zone_file_cache_test.go
+++ b/pkg/zonemgr/zone_file_cache_test.go
@@ -1,10 +1,9 @@
 package zonemgr
 
 import (
+	"fmt"
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
-
-	"fmt"
 	"sort"
 	"strings"
 
@@ -32,11 +31,11 @@ var _ = Describe("cached zone file content maintenance", func() {
 		)
 
 		DescribeTable("generate zone file header", func(nameServerIP, domain, expectedHeader string) {
-			zoneFileCache = NewZoneFileCache(nameServerIP, domain)
+			zoneFileCache = NewZoneFileCache(nameServerIP, domain, 0)
 			Expect(zoneFileCache.header).To(Equal(expectedHeader))
 		},
-			Entry("header should contain default values", "", "", headerDefault),
-			Entry("header should contain custom values", nameServerIP, domain, headerCustom),
+			Entry("header should contain default values", "", "vm", headerDefault),
+			Entry("header should contain custom values", nameServerIP, "vm."+domain, headerCustom),
 		)
 	})
 
@@ -86,7 +85,7 @@ var _ = Describe("cached zone file content maintenance", func() {
 
 		When("interfaces records list is empty", func() {
 			BeforeEach(func() {
-				zoneFileCache = NewZoneFileCache(nameServerIP, domain)
+				zoneFileCache = NewZoneFileCache(nameServerIP, domain, 0)
 			})
 
 			DescribeTable("Updating interfaces records", validateUpdateFunc,
@@ -111,7 +110,7 @@ var _ = Describe("cached zone file content maintenance", func() {
 
 		When("interfaces records list contains single vmi", func() {
 			BeforeEach(func() {
-				zoneFileCache = NewZoneFileCache(nameServerIP, domain)
+				zoneFileCache = NewZoneFileCache(nameServerIP, domain, 0)
 				isUpdated := zoneFileCache.updateVMIRecords(k8stypes.NamespacedName{Namespace: namespace1, Name: vmi1Name},
 					[]v1.VirtualMachineInstanceNetworkInterface{{IPs: []string{nic1IP}, Name: nic1Name}, {IPs: []string{nic2IP}, Name: nic2Name}})
 				Expect(isUpdated).To(BeTrue())
@@ -160,7 +159,7 @@ var _ = Describe("cached zone file content maintenance", func() {
 
 		When("interfaces records list contains multiple vmis", func() {
 			BeforeEach(func() {
-				zoneFileCache = NewZoneFileCache(nameServerIP, domain)
+				zoneFileCache = NewZoneFileCache(nameServerIP, domain, 0)
 				isUpdated := zoneFileCache.updateVMIRecords(k8stypes.NamespacedName{Namespace: namespace1, Name: vmi1Name},
 					[]v1.VirtualMachineInstanceNetworkInterface{{IPs: []string{nic1IP}, Name: nic1Name}, {IPs: []string{nic2IP}, Name: nic2Name}})
 				Expect(isUpdated).To(BeTrue())
@@ -219,7 +218,7 @@ var _ = Describe("cached zone file content maintenance", func() {
 
 		When("interfaces records list contains vmi with multiple IPs", func() {
 			BeforeEach(func() {
-				zoneFileCache = NewZoneFileCache(nameServerIP, domain)
+				zoneFileCache = NewZoneFileCache(nameServerIP, domain, 0)
 			})
 
 			DescribeTable("Updating interfaces records list", validateUpdateFunc,
diff --git a/pkg/zonemgr/zone_file_test.go b/pkg/zonemgr/zone_file_test.go
index 259ef6a..b592d0d 100644
--- a/pkg/zonemgr/zone_file_test.go
+++ b/pkg/zonemgr/zone_file_test.go
@@ -13,6 +13,7 @@ var _ = Describe("disk zone file maintenance", func() {
 		zoneFileName           = "zones/db.vm"
 		zoneFileContent        = "zone file content"
 		zoneFileUpdatedContent = "zone file updated content"
+		headerSoaSerial        = "$ORIGIN vm. \n$TTL 3600 \n@ IN SOA ns.vm. email.vm. (12345 3600 3600 1209600 3600)\n"
 	)
 	var zoneFile *ZoneFile
 
@@ -42,15 +43,18 @@ var _ = Describe("disk zone file maintenance", func() {
 	})
 
 	When("zone file already exist", func() {
-		BeforeEach(func() {
-			Expect(os.WriteFile(zoneFileName, []byte(zoneFileContent), zoneFilePerm)).To(Succeed())
-		})
 		AfterEach(func() {
 			Expect(os.RemoveAll(zoneFileName)).To(Succeed())
 		})
 
 		It("should override a zone file on disk", func() {
+			Expect(os.WriteFile(zoneFileName, []byte(zoneFileContent), zoneFilePerm)).To(Succeed())
 			testFileFunc(zoneFileUpdatedContent)
 		})
+
+		It("should read SOA serial", func() {
+			Expect(os.WriteFile(zoneFileName, []byte(headerSoaSerial), 0777)).To(Succeed())
+			Expect(zoneFile.ReadSoaSerial()).To(Equal(12345))
+		})
 	})
 })
diff --git a/pkg/zonemgr/zone_manager_test.go b/pkg/zonemgr/zone_manager_test.go
index 22f84df..d9238f7 100644
--- a/pkg/zonemgr/zone_manager_test.go
+++ b/pkg/zonemgr/zone_manager_test.go
@@ -41,11 +41,5 @@ var _ = Describe("Zone Manager functionality", func() {
 		It("should create zone file with correct name", func() {
 			Expect(zoneMgr.zoneFile.zoneFileFullName).To(Equal("/zones/db.vm." + customDomain))
 		})
-
-		When("zone file already exist", func() {
-			It("should update cached SOA serial value", func() {
-				//TODO
-			})
-		})
 	})
 })