now build failed error resolved

Author: Divyansh Saxena

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

@@ -7,6 +7,13 @@
 
 public class KMPTest {
 
+    @Test
+    public void testNullInputs() {
+        assertEquals(List.of(), KMP.kmpMatcher(null, "A"));
+        assertEquals(List.of(), KMP.kmpMatcher("A", null));
+        assertEquals(List.of(), KMP.kmpMatcher(null, null));
+    }
+
     @Test
     public void testKMPMatcher() {
         assertEquals(List.of(0, 1), KMP.kmpMatcher("AAAAABAAABA", "AAAA"));

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

@@ -7,6 +7,30 @@
 
 public class RabinKarpTest {
 
+    @Test
+    public void testNullInputs() {
+        assertEquals(List.of(), RabinKarp.search(null, "A"));
+        assertEquals(List.of(), RabinKarp.search("A", null));
+        assertEquals(List.of(), RabinKarp.search(null, null));
+    }
+
+    @Test
+    public void testHashCollision() {
+        // 'a' = 97. (char)198 % 101 = 97.
+        // For length 1, h = 1. p = 97. t = 198 % 101 = 97.
+        // Collision occurs, loop checks characters: 198 != 97, breaks.
+        char collisionChar = (char) 198;
+        String text = String.valueOf(collisionChar);
+        String pattern = "a";
+        assertEquals(List.of(), RabinKarp.search(text, pattern));
+    }
+
+    @Test
+    public void testSearchWithCustomQ() {
+        // Using a different prime
+        assertEquals(List.of(0, 1), RabinKarp.search("AAAA", "AAA", 13));
+    }
+
     @Test
     public void testRabinKarpSearch() {
         assertEquals(List.of(0, 1), RabinKarp.search("AAAAABAAABA", "AAAA"));