diff --git a/src/main/java/seedu/address/model/contact/Role.java b/src/main/java/seedu/address/model/contact/Role.java
index 75b684d09f3..67368dc8e38 100644
--- a/src/main/java/seedu/address/model/contact/Role.java
+++ b/src/main/java/seedu/address/model/contact/Role.java
@@ -66,7 +66,7 @@ public Role(String roleName) {
     public static boolean isValidRoleName(String test) {
         requireNonNull(test);
         return Arrays.stream(AVAILABLE_ROLES)
-                .map(role -> role.toLowerCase())
+                .map(String::toLowerCase)
                 .anyMatch(role -> role.equals(test.trim().toLowerCase()));
     }
 
@@ -82,13 +82,7 @@ private String toOfficialCase(String input) {
     }
 
     private int assignRoleIndex(String roleName) {
-        assert roleName.equals(PRESIDENT) // must be case sensitive
-                || roleName.equals(VICE_PRESIDENT)
-                || roleName.equals(ADMIN)
-                || roleName.equals(MARKETING)
-                || roleName.equals(EVENTS_INTERNAL)
-                || roleName.equals(EVENTS_EXTERNAL)
-                || roleName.equals(EXTERNAL_RELATIONS);
+        assert Arrays.asList(AVAILABLE_ROLES).contains(roleName);
 
         int errorStatus = -1;
 
diff --git a/src/main/java/seedu/address/ui/PaginationPanel.java b/src/main/java/seedu/address/ui/PaginationPanel.java
index 92a421a0923..f8420144853 100644
--- a/src/main/java/seedu/address/ui/PaginationPanel.java
+++ b/src/main/java/seedu/address/ui/PaginationPanel.java
@@ -1,12 +1,16 @@
 package seedu.address.ui;
 
+import static java.util.Objects.requireNonNull;
+
 import java.util.List;
+import java.util.logging.Logger;
 
 import javafx.collections.FXCollections;
 import javafx.collections.ListChangeListener;
 import javafx.collections.ObservableList;
 import javafx.scene.Node;
 import javafx.scene.control.Pagination;
+import seedu.address.commons.core.LogsCenter;
 import seedu.address.model.contact.Contact;
 
 /**
@@ -15,6 +19,7 @@
 public class PaginationPanel extends Pagination {
     public static final int ROWS_PER_PAGE = 10;
     private static int currentPageIndex = 0;
+    private static final Logger logger = LogsCenter.getLogger(PaginationPanel.class);
     private final ObservableList<Contact> contactList;
 
     /**
@@ -23,8 +28,9 @@ public class PaginationPanel extends Pagination {
      */
     public PaginationPanel(ObservableList<Contact> contactList) {
         super();
+        requireNonNull(contactList);
         this.contactList = contactList;
-        this.contactList.addListener(this::onListItemsChanged); // enables UI update to ContactPagination
+        this.contactList.addListener(this::onListItemsChanged);
         this.initPagination();
     }
 
@@ -34,18 +40,21 @@ public PaginationPanel(ObservableList<Contact> contactList) {
      * @return The index of the item in {@code contactList}.
      */
     public static int convertItemIndexToDisplayIndex(int itemIndex) {
-        return (currentPageIndex) * ROWS_PER_PAGE + itemIndex + 1;
+        assert itemIndex >= 0;
+        return currentPageIndex * ROWS_PER_PAGE + itemIndex + 1;
     }
 
     private void initPagination() {
         final int minPageCount = 1;
-        int pageCount = Math.max((int) Math.ceil((double) contactList.size() / ROWS_PER_PAGE), minPageCount);
+        int expectedPageCount = (int) Math.ceil((double) contactList.size() / ROWS_PER_PAGE);
+        int pageCount = Math.max(expectedPageCount, minPageCount);
         this.setPageCount(pageCount);
-        this.setStyle("-fx-page-information-alignment: bottom;");
         this.setPageFactory(this::createPage);
+        logger.info("A pagination which contains " + pageCount + " page(s) has been created.");
     }
 
     private Node createPage(int pageIndex) {
+        assert pageIndex >= 0;
         PaginationPanel.currentPageIndex = pageIndex;
         int fromIndex = pageIndex * PaginationPanel.ROWS_PER_PAGE;
         int endIndex = Math.min(fromIndex + PaginationPanel.ROWS_PER_PAGE, contactList.size());
@@ -59,5 +68,6 @@ private Node createPage(int pageIndex) {
 
     private void onListItemsChanged(ListChangeListener.Change<? extends Contact> unused) {
         this.initPagination();
+        logger.info("Re-render pagination due to the change of list items.");
     }
 }