Add JUnit tests for LengthOfLastWord algorithm

Author: gopaljilab

src/test/java/com/thealgorithms/strings/LengthOfLastWordTest.java

@@ -1,4 +1,18 @@
 package com.thealgorithms.strings;
 
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 public class LengthOfLastWordTest {
+    @Test
+    public void testLengthOfLastWord() {
+        assertEquals(5, new LengthOfLastWord().lengthOfLastWord("Hello World"));
+        assertEquals(4, new LengthOfLastWord().lengthOfLastWord("  fly me   to   the moon  "));
+        assertEquals(6, new LengthOfLastWord().lengthOfLastWord("luffy is still joyboy"));
+        assertEquals(5, new LengthOfLastWord().lengthOfLastWord("Hello"));
+        assertEquals(0, new LengthOfLastWord().lengthOfLastWord("     "));
+        assertEquals(0, new LengthOfLastWord().lengthOfLastWord(""));
+        assertEquals(3, new LengthOfLastWord().lengthOfLastWord("JUST LIE  "));
+    }
 }