diff --git a/src/test/java/org/opensearch/security/dlic/rest/api/ActionGroupsApiTest.java b/src/test/java/org/opensearch/security/dlic/rest/api/ActionGroupsApiTest.java
index b2d985b189..3b20e6d839 100644
--- a/src/test/java/org/opensearch/security/dlic/rest/api/ActionGroupsApiTest.java
+++ b/src/test/java/org/opensearch/security/dlic/rest/api/ActionGroupsApiTest.java
@@ -30,6 +30,8 @@
 import org.opensearch.security.test.helper.rest.RestHelper.HttpResponse;
 import com.google.common.collect.ImmutableList;
 
+import static org.opensearch.security.dlic.rest.api.RolesApiTest.EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG;
+
 @RunWith(Parameterized.class)
 public class ActionGroupsApiTest extends AbstractRestApiUnitTest {
 
@@ -385,6 +387,6 @@ public void checkNullElementsInArray() throws Exception{
         String body = FileHelper.loadFile("restapi/actiongroup_null_array_element.json");
         HttpResponse response = rh.executePutRequest(ENDPOINT + "/CRUD_UT", body, new Header[0]);
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-        Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+        Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
     }
 }
diff --git a/src/test/java/org/opensearch/security/dlic/rest/api/NodesDnApiTest.java b/src/test/java/org/opensearch/security/dlic/rest/api/NodesDnApiTest.java
index c8c3819da8..8da6cb2ff6 100644
--- a/src/test/java/org/opensearch/security/dlic/rest/api/NodesDnApiTest.java
+++ b/src/test/java/org/opensearch/security/dlic/rest/api/NodesDnApiTest.java
@@ -40,6 +40,7 @@
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
+import static org.opensearch.security.dlic.rest.api.RolesApiTest.EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG;
 
 @RunWith(Parameterized.class)
 public class NodesDnApiTest extends AbstractRestApiUnitTest {
@@ -122,7 +123,7 @@ private void checkNullElementsInArray(final Header headers) throws Exception{
         String body = FileHelper.loadFile("restapi/nodesdn_null_array_element.json");
         HttpResponse response = rh.executePutRequest(ENDPOINT + "/nodesdn/cluster1", body, headers);
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-        Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+        Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
     }
 
     @Test
diff --git a/src/test/java/org/opensearch/security/dlic/rest/api/RolesApiTest.java b/src/test/java/org/opensearch/security/dlic/rest/api/RolesApiTest.java
index fff42682c5..a9fb94ff6e 100644
--- a/src/test/java/org/opensearch/security/dlic/rest/api/RolesApiTest.java
+++ b/src/test/java/org/opensearch/security/dlic/rest/api/RolesApiTest.java
@@ -36,6 +36,7 @@
 @RunWith(Parameterized.class)
 public class RolesApiTest extends AbstractRestApiUnitTest {
 
+    public final static String EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG = "`null` is not allowed as json array element";
     private final String ENDPOINT;
 
     public RolesApiTest(String endpoint){
@@ -532,32 +533,32 @@ public void checkNullElementsInArray() throws Exception{
         String body = FileHelper.loadFile("restapi/roles_null_array_element_cluster_permissions.json");
         HttpResponse response = rh.executePutRequest(ENDPOINT + "/roles/opendistro_security_role_starfleet", body, new Header[0]);
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-        Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+        Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
 
         body = FileHelper.loadFile("restapi/roles_null_array_element_index_permissions.json");
         response = rh.executePutRequest(ENDPOINT+ "/roles/opendistro_security_role_starfleet", body, new Header[0]);
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-        Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+        Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
 
         body = FileHelper.loadFile("restapi/roles_null_array_element_tenant_permissions.json");
         response = rh.executePutRequest(ENDPOINT + "/roles/opendistro_security_role_starfleet", body, new Header[0]);
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-        Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+        Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
 
         body = FileHelper.loadFile("restapi/roles_null_array_element_index_patterns.json");
         response = rh.executePutRequest(ENDPOINT + "/roles/opendistro_security_role_starfleet", body, new Header[0]);
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-        Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+        Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
 
         body = FileHelper.loadFile("restapi/roles_null_array_element_masked_fields.json");
         response = rh.executePutRequest(ENDPOINT + "/roles/opendistro_security_role_starfleet", body, new Header[0]);
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-        Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+        Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
 
         body = FileHelper.loadFile("restapi/roles_null_array_element_allowed_actions.json");
         response = rh.executePutRequest(ENDPOINT + "/roles/opendistro_security_role_starfleet", body, new Header[0]);
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-        Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+        Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
     }
 
 }
diff --git a/src/test/java/org/opensearch/security/dlic/rest/api/RolesMappingApiTest.java b/src/test/java/org/opensearch/security/dlic/rest/api/RolesMappingApiTest.java
index 17a7453070..5ee187737a 100644
--- a/src/test/java/org/opensearch/security/dlic/rest/api/RolesMappingApiTest.java
+++ b/src/test/java/org/opensearch/security/dlic/rest/api/RolesMappingApiTest.java
@@ -32,6 +32,8 @@
 import org.opensearch.security.test.helper.rest.RestHelper.HttpResponse;
 import com.google.common.collect.ImmutableList;
 
+import static org.opensearch.security.dlic.rest.api.RolesApiTest.EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG;
+
 @RunWith(Parameterized.class)
 public class RolesMappingApiTest extends AbstractRestApiUnitTest {
 
@@ -422,18 +424,18 @@ public void checkNullElementsInArray() throws Exception{
 		HttpResponse response = rh.executePutRequest(ENDPOINT + "/rolesmapping/opendistro_security_role_starfleet_captains",
 													 body, new Header[0]);
 		Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-		Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+		Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
 
 		body = FileHelper.loadFile("restapi/rolesmapping_null_array_element_backend_roles.json");
 		response = rh.executePutRequest(ENDPOINT + "/rolesmapping/opendistro_security_role_starfleet_captains",
 													 body, new Header[0]);
 		Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-		Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+		Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
 
 		body = FileHelper.loadFile("restapi/rolesmapping_null_array_element_hosts.json");
 		response = rh.executePutRequest(ENDPOINT + "/rolesmapping/opendistro_security_role_starfleet_captains",
 										 body, new Header[0]);
 		Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-		Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+		Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
 	}
 }
diff --git a/src/test/java/org/opensearch/security/dlic/rest/api/UserApiTest.java b/src/test/java/org/opensearch/security/dlic/rest/api/UserApiTest.java
index 548f0323ad..521ca55447 100644
--- a/src/test/java/org/opensearch/security/dlic/rest/api/UserApiTest.java
+++ b/src/test/java/org/opensearch/security/dlic/rest/api/UserApiTest.java
@@ -34,6 +34,8 @@
 import com.google.common.collect.ImmutableList;
 import java.util.List;
 
+import static org.opensearch.security.dlic.rest.api.RolesApiTest.EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG;
+
 @RunWith(Parameterized.class)
 public class UserApiTest extends AbstractRestApiUnitTest {
 
@@ -647,7 +649,7 @@ public void checkNullElementsInArray() throws Exception{
         String body = FileHelper.loadFile("restapi/users_null_array_element.json");
         HttpResponse response = rh.executePutRequest(ENDPOINT + "/internalusers/picard", body, new Header[0]);
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-        Assert.assertTrue(response.getBody().contains("`null` is not allowed as json array element"));
+        Assert.assertTrue(response.getBody().contains(EXPECTED_NULL_ELEMENT_IN_ARRAY_MSG));
     }
 
 }