diff --git a/algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/string/LongestSubstringNonRepeatingCharacters.java b/algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/string/LongestSubstringNonRepeatingCharacters.java
index 51ae013cd6..cd1f3e94d5 100644
--- a/algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/string/LongestSubstringNonRepeatingCharacters.java
+++ b/algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/string/LongestSubstringNonRepeatingCharacters.java
@@ -44,8 +44,11 @@ public class LongestSubstringNonRepeatingCharacters {
     }
 
     public static void main(String[] args) {
-        String input = "CODINGISAWESOME";
-        System.out.println(getUniqueCharacterSubstring(input));
+        if(args.length > 0) {
+            System.out.println(getUniqueCharacterSubstring(args[0]));
+        } else {
+            System.err.println("This program expects command-line input. Please try again!");
+        }
     }
 
 }
diff --git a/algorithms-miscellaneous-1/src/test/java/com/baeldung/algorithms/string/LongestSubstringNonRepeatingCharactersTest.java b/algorithms-miscellaneous-1/src/test/java/com/baeldung/algorithms/string/LongestSubstringNonRepeatingCharactersTest.java
index 2d8e762dd1..2150be2532 100644
--- a/algorithms-miscellaneous-1/src/test/java/com/baeldung/algorithms/string/LongestSubstringNonRepeatingCharactersTest.java
+++ b/algorithms-miscellaneous-1/src/test/java/com/baeldung/algorithms/string/LongestSubstringNonRepeatingCharactersTest.java
@@ -1,20 +1,31 @@
 package com.baeldung.algorithms.string;
 
-import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static com.baeldung.algorithms.string.LongestSubstringNonRepeatingCharacters.getUniqueCharacterSubstring;
+import static com.baeldung.algorithms.string.LongestSubstringNonRepeatingCharacters.getUniqueCharacterSubstringBruteForce;
+
 public class LongestSubstringNonRepeatingCharactersTest {
 
     @Test
     void givenString_whenGetUniqueCharacterSubstringBruteForceCalled_thenResultFoundAsExpected() {
-        String input = "CODINGISAWESOME";
-        Assertions.assertEquals("NGISAWE", LongestSubstringNonRepeatingCharacters.getUniqueCharacterSubstringBruteForce(input));
+        assertEquals("", getUniqueCharacterSubstringBruteForce(""));
+        assertEquals("A", getUniqueCharacterSubstringBruteForce("A"));
+        assertEquals("ABCDEF", getUniqueCharacterSubstringBruteForce("AABCDEF"));
+        assertEquals("ABCDEF", getUniqueCharacterSubstringBruteForce("ABCDEFF"));
+        assertEquals("NGISAWE", getUniqueCharacterSubstringBruteForce("CODINGISAWESOME"));
+        assertEquals("be coding", getUniqueCharacterSubstringBruteForce("always be coding"));
     }
 
     @Test
     void givenString_whenGetUniqueCharacterSubstringCalled_thenResultFoundAsExpected() {
-        String input = "CODINGISAWESOME";
-        Assertions.assertEquals("NGISAWE",LongestSubstringNonRepeatingCharacters.getUniqueCharacterSubstring(input));
+        assertEquals("", getUniqueCharacterSubstring(""));
+        assertEquals("A", getUniqueCharacterSubstring("A"));
+        assertEquals("ABCDEF", getUniqueCharacterSubstring("AABCDEF"));
+        assertEquals("ABCDEF", getUniqueCharacterSubstring("ABCDEFF"));
+        assertEquals("NGISAWE", getUniqueCharacterSubstring("CODINGISAWESOME"));
+        assertEquals("be coding", getUniqueCharacterSubstring("always be coding"));
     }
 
 }