test: added test cases for Z Algorithm

Author: Mrinal Chauhan

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

@@ -0,0 +1,60 @@
+package com.thealgorithms.strings;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+public class ZalgorithmTest {
+    /**
+     * Test 1:
+     * Input: text = "ababcababcabc", pattern = "abc"
+     * Output: [2, 7, 10]
+     * Explanation: The pattern "abc" occurs at indices 2, 7, and 10.
+     */
+    @Test
+    public void testFindPatternOccurrences() {
+        String text = "ababcababcabc";
+        String pattern = "abc";
+        List<Integer> expected = Arrays.asList(2, 7, 10);
+        
+        List<Integer> actual = Zalgorithm.findPatternOccurrences(text, pattern);
+        
+        assertEquals(expected, actual);
+    }
+
+    /**
+     * Test 2:
+     * Input: text = "abcdefg", pattern = "xyz"
+     * Output: []
+     * Explanation: The pattern "xyz" does not occur in the text.
+     */
+    @Test
+    public void testFindPatternOccurrencesNoMatch() {
+        String text = "abcdefg";
+        String pattern = "xyz";
+        List<Integer> expected = Arrays.asList();
+        
+        List<Integer> actual = Zalgorithm.findPatternOccurrences(text, pattern);
+        
+        assertEquals(expected, actual);
+    }
+
+    /**
+     * Test 3:
+     * Input: text = "aabbaabbaaa", pattern = "a"
+     * Output: [0, 3, 5, 9]
+     * Explanation: The pattern "a" occurs at indices 0, 3, 5, and 9.
+     */
+    @Test
+    public void testFindPatternOccurrencesSingleCharacter() {
+        String text = "aabbaabbaaa";
+        String pattern = "a";
+        List<Integer> expected = Arrays.asList(0, 3, 5, 9);
+        
+        List<Integer> actual = Zalgorithm.findPatternOccurrences(text, pattern);
+        
+        assertEquals(expected, actual);
+    }
+}