diff --git a/libraries/src/main/java/com/baeldung/commons/collectionutil/Address.java b/libraries/src/main/java/com/baeldung/commons/collectionutil/Address.java
index d046f0f8aa..a1e231ec85 100644
--- a/libraries/src/main/java/com/baeldung/commons/collectionutil/Address.java
+++ b/libraries/src/main/java/com/baeldung/commons/collectionutil/Address.java
@@ -2,9 +2,9 @@ package com.baeldung.commons.collectionutil;
 
 public class Address {
 
-    String locality;
-    String city;
-    String zip;
+    private String locality;
+    private String city;
+    private String zip;
 
     public String getLocality() {
         return locality;
diff --git a/libraries/src/main/java/com/baeldung/commons/collectionutil/Customer.java b/libraries/src/main/java/com/baeldung/commons/collectionutil/Customer.java
index 2d3be36143..e22f13861e 100644
--- a/libraries/src/main/java/com/baeldung/commons/collectionutil/Customer.java
+++ b/libraries/src/main/java/com/baeldung/commons/collectionutil/Customer.java
@@ -2,12 +2,12 @@ package com.baeldung.commons.collectionutil;
 
 public class Customer implements Comparable<Customer> {
 
-    Integer id;
-    String name;
-    Long phone;
-    String locality;
-    String city;
-    String zip;
+    private Integer id;
+    private String name;
+    private Long phone;
+    private String locality;
+    private String city;
+    private String zip;
 
     public Integer getId() {
         return id;
diff --git a/libraries/src/test/java/com/baeldung/commons/collections/CollectionUtilsGuideTest.java b/libraries/src/test/java/com/baeldung/commons/collections/CollectionUtilsGuideTest.java
index d7474b4d20..9166865484 100644
--- a/libraries/src/test/java/com/baeldung/commons/collections/CollectionUtilsGuideTest.java
+++ b/libraries/src/test/java/com/baeldung/commons/collections/CollectionUtilsGuideTest.java
@@ -12,6 +12,7 @@ import org.junit.Test;
 
 import java.util.*;
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
@@ -45,6 +46,8 @@ public class CollectionUtilsGuideTest {
     @Test
     public void givenTwoSortedLists_whenCollated_thenSorted() {
         List<Customer> sortedList = CollectionUtils.collate(list1, list2);
+
+        assertEquals(6, sortedList.size());
         assertTrue(sortedList.get(0).getName().equals("Bob"));
         assertTrue(sortedList.get(2).getName().equals("Daniel"));
     }
@@ -61,7 +64,7 @@ public class CollectionUtilsGuideTest {
     }
     
     @Test
-    public void givenCustomerList_WhenFiltered_thenCorrectSize() {
+    public void givenCustomerList_whenFiltered_thenCorrectSize() {
         
         boolean isModified = CollectionUtils.filter(linkedList1, customer -> Arrays.asList("Daniel","Kyle").contains(customer.getName()));