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 3c0466297b..ec5b0a15f7 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
@@ -384,6 +384,8 @@ 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]);
+        Settings settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+        Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
     }
 }
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 f7d9bf6d8a..ffc9a0cfa5 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
@@ -15,6 +15,7 @@
 
 package org.opensearch.security.dlic.rest.api;
 
+import org.opensearch.common.xcontent.XContentType;
 import org.opensearch.security.auditlog.impl.AuditCategory;
 import org.opensearch.security.auditlog.impl.AuditMessage;
 import org.opensearch.security.auditlog.integration.TestAuditlogImpl;
@@ -30,6 +31,7 @@
 import org.junit.runners.Parameterized;
 import org.opensearch.security.test.helper.rest.RestHelper.HttpResponse;
 import org.opensearch.security.test.helper.file.FileHelper;
+import org.opensearch.security.dlic.rest.validation.AbstractConfigurationValidator;
 
 import java.util.Arrays;
 import java.util.List;
@@ -41,6 +43,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
 
+
 @RunWith(Parameterized.class)
 public class NodesDnApiTest extends AbstractRestApiUnitTest {
     private HttpResponse response;
@@ -117,6 +120,15 @@ private void testCrudScenarios(final int expectedStatus, final Header... headers
         assertThat(response.getBody(), response.getStatusCode(), equalTo(expectedStatus));
     }
 
+    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);
+        Settings settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
+        Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+        Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
+    }
+
     @Test
     public void testNodesDnApiWithDynamicConfigDisabled() throws Exception {
         setup();
@@ -158,6 +170,12 @@ public void testNodesDnApi() throws Exception {
             testCrudScenarios(HttpStatus.SC_OK, nonAdminCredsHeader);
         }
 
+        {
+            rh.keystore = "restapi/kirk-keystore.jks";
+            rh.sendAdminCertificate = true;
+            checkNullElementsInArray(nonAdminCredsHeader);
+        }
+
         {
             // any creds, admin certificate, disallowed key - FORBIDDEN
             rh.keystore = "restapi/kirk-keystore.jks";
@@ -214,14 +232,4 @@ public void testNodesDnApiAuditComplianceLogging() throws Exception {
         assertThat(actualCategoryCounts, equalTo(expectedCategoryCounts));
     }
 
-    @Test
-    public void checkNullElementsInArray() throws Exception{
-        setup();
-        rh.keystore = "restapi/kirk-keystore.jks";
-        rh.sendAdminCertificate = true;
-
-        String body = FileHelper.loadFile("restapi/nodesdn_null_array_element.json");
-        HttpResponse response = rh.executePutRequest(ENDPOINT+ "/nodesdn", body, new Header[0]);
-        Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
-    }
 }
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 83a6f9254a..bb290c0079 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
@@ -19,6 +19,8 @@
 
 import org.junit.runner.RunWith;
 import org.junit.runners.Parameterized;
+import org.opensearch.common.settings.Settings;
+import org.opensearch.common.xcontent.XContentType;
 import org.opensearch.security.DefaultObjectMapper;
 import org.apache.http.Header;
 import org.apache.http.HttpStatus;
@@ -27,7 +29,6 @@
 
 import com.fasterxml.jackson.databind.JsonNode;
 import org.opensearch.security.dlic.rest.validation.AbstractConfigurationValidator;
-import org.opensearch.security.dlic.rest.validation.AbstractConfigurationValidator.ErrorType;
 import org.opensearch.security.support.SecurityJsonNode;
 import org.opensearch.security.test.helper.file.FileHelper;
 import org.opensearch.security.test.helper.rest.RestHelper.HttpResponse;
@@ -365,7 +366,7 @@ public void testRolesApi() throws Exception {
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
         settings = DefaultObjectMapper.readTree(response.getBody());
         Assert.assertEquals(settings.get("status").asText(), "error");
-        Assert.assertEquals(settings.get("reason").asText(), ErrorType.INVALID_CONFIGURATION.getMessage());
+        Assert.assertEquals(settings.get("reason").asText(), AbstractConfigurationValidator.ErrorType.INVALID_CONFIGURATION.getMessage());
 
         // -- PATCH
         // PATCH on non-existing resource
@@ -531,27 +532,39 @@ 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]);
+        Settings settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+        Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
 
         body = FileHelper.loadFile("restapi/roles_null_array_element_index_permissions.json");
         response = rh.executePutRequest(ENDPOINT+ "/roles/opendistro_security_role_starfleet", body, new Header[0]);
+        settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+        Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
 
         body = FileHelper.loadFile("restapi/roles_null_array_element_tenant_permissions.json");
         response = rh.executePutRequest(ENDPOINT + "/roles/opendistro_security_role_starfleet", body, new Header[0]);
+        settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+        Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
 
         body = FileHelper.loadFile("restapi/roles_null_array_element_index_patterns.json");
         response = rh.executePutRequest(ENDPOINT + "/roles/opendistro_security_role_starfleet", body, new Header[0]);
+        settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+        Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
 
         body = FileHelper.loadFile("restapi/roles_null_array_element_masked_fields.json");
         response = rh.executePutRequest(ENDPOINT + "/roles/opendistro_security_role_starfleet", body, new Header[0]);
+        settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+        Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
 
         body = FileHelper.loadFile("restapi/roles_null_array_element_allowed_actions.json");
         response = rh.executePutRequest(ENDPOINT + "/roles/opendistro_security_role_starfleet", body, new Header[0]);
+        settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+        Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
     }
 
 }
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 65d6750f57..30887a7fad 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
@@ -15,7 +15,6 @@
 
 package org.opensearch.security.dlic.rest.api;
 
-import java.util.Arrays;
 import java.util.List;
 
 import org.apache.http.Header;
@@ -421,16 +420,22 @@ public void checkNullElementsInArray() throws Exception{
 		String body = FileHelper.loadFile("restapi/rolesmapping_null_array_element_users.json");
 		HttpResponse response = rh.executePutRequest(ENDPOINT + "/rolesmapping/opendistro_security_role_starfleet_captains",
 													 body, new Header[0]);
+		Settings settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
 		Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+		Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
 
 		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]);
+		settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
 		Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+		Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
 
 		body = FileHelper.loadFile("restapi/rolesmapping_null_array_element_hosts.json");
 		response = rh.executePutRequest(ENDPOINT + "/rolesmapping/opendistro_security_role_starfleet_captains",
 										 body, new Header[0]);
+		settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
 		Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+		Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
 	}
 }
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 abb329f088..afa5930e58 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
@@ -646,7 +646,9 @@ 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]);
+        Settings settings = Settings.builder().loadFromSource(response.getBody(), XContentType.JSON).build();
         Assert.assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatusCode());
+        Assert.assertEquals(AbstractConfigurationValidator.ErrorType.NULL_ARRAY_ELEMENT.getMessage(), settings.get("reason"));
     }
 
 }