diff --git a/pom.xml b/pom.xml
index 938fb41088dc..9319178c0bf2 100644
--- a/pom.xml
+++ b/pom.xml
@@ -55,6 +55,13 @@
             <artifactId>commons-collections4</artifactId>
             <version>4.5.0</version>
         </dependency>
+
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.9.3</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
diff --git a/src/main/java/com/thealgorithms/strings/Alphabetical.java b/src/main/java/com/thealgorithms/strings/Alphabetical.java
index ef2974eb427d..7abc9abfb3bb 100644
--- a/src/main/java/com/thealgorithms/strings/Alphabetical.java
+++ b/src/main/java/com/thealgorithms/strings/Alphabetical.java
@@ -21,12 +21,17 @@ private Alphabetical() {
      * @return {@code true} if all characters are in alphabetical order (case-insensitive), otherwise {@code false}
      */
     public static boolean isAlphabetical(String s) {
+        if (s == null || s.isEmpty()) {
+            return false;
+        }
         s = s.toLowerCase();
-        for (int i = 0; i < s.length() - 1; ++i) {
-            if (!Character.isLetter(s.charAt(i)) || s.charAt(i) > s.charAt(i + 1)) {
+        for (int i = 0; i < s.length() - 1; i++) {
+            char current = s.charAt(i);
+            char next = s.charAt(i + 1);
+            if (!Character.isLetter(current) || current > next) {
                 return false;
             }
         }
-        return !s.isEmpty() && Character.isLetter(s.charAt(s.length() - 1));
+        return Character.isLetter(s.charAt(s.length() - 1));
     }
 }
diff --git a/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java b/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java
index 7b41e11ef22f..a3f8afa8160c 100644
--- a/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java
+++ b/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java
@@ -8,8 +8,23 @@
 public class AlphabeticalTest {
 
     @ParameterizedTest(name = "\"{0}\" → Expected: {1}")
-    @CsvSource({"'abcdefghijklmno', true", "'abcdxxxyzzzz', true", "'123a', false", "'abcABC', false", "'abcdefghikjlmno', false", "'aBC', true", "'abc', true", "'xyzabc', false", "'abcxyz', true", "'', false", "'1', false"})
+    @CsvSource({
+            "'abcdefghijklmno', true",
+            "'abcdxxxyzzzz', true",
+            "'123a', false",
+            "'abcABC', false",
+            "'abcdefghikjlmno', false",
+            "'aBC', true",
+            "'abc', true",
+            "'xyzabc', false",
+            "'abcxyz', true",
+            "'', false",
+            "'1', false",
+            "'abc!', false",   // <-- missing coverage
+            "'ABc1', false"    // <-- optional extra
+    })
     void testIsAlphabetical(String input, boolean expected) {
         assertEquals(expected, Alphabetical.isAlphabetical(input));
     }
+
 }