Add tests for HorspoolSearch (#4165)

src/main/java/com/thealgorithms/strings/HorspoolSearch.java

@@ -100,6 +100,10 @@ public class HorspoolSearch {
         shiftValues = calcShiftValues(pattern); // build the bad symbol table
         comparisons = 0; // reset comparisons
 
+        if (pattern.length() == 0) { // return failure, if pattern empty
+            return -1;
+        }
+
         int textIndex = pattern.length() - 1; // align pattern with text start and get index of the last character
 
         // while pattern is not out of text bounds

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

@@ -0,0 +1,88 @@
+package com.thealgorithms.strings;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class HorspoolSearchTest {
+
+    @Test
+    void testFindFirstMatch() {
+        int index = HorspoolSearch.findFirst("World", "Hello World");
+        assertEquals(6, index);
+    }
+
+    @Test
+    void testFindFirstNotMatch() {
+        int index = HorspoolSearch.findFirst("hell", "Hello World");
+        assertEquals(-1, index);
+    }
+
+    @Test
+    void testFindFirstPatternLongerText() {
+        int index = HorspoolSearch.findFirst("Hello World!!!", "Hello World");
+        assertEquals(-1, index);
+    }
+
+    @Test
+    void testFindFirstPatternEmpty() {
+        int index = HorspoolSearch.findFirst("", "Hello World");
+        assertEquals(-1, index);
+    }
+
+    @Test
+    void testFindFirstTextEmpty() {
+        int index = HorspoolSearch.findFirst("Hello", "");
+        assertEquals(-1, index);
+    }
+
+    @Test
+    void testFindFirstPatternAndTextEmpty() {
+        int index = HorspoolSearch.findFirst("", "");
+        assertEquals(-1, index);
+    }
+
+    @Test
+    void testFindFirstSpecialCharacter() {
+        int index = HorspoolSearch.findFirst("$3**", "Hello $3**$ World");
+        assertEquals(6, index);
+    }
+
+    @Test
+    void testFindFirstInsensitiveMatch() {
+        int index = HorspoolSearch.findFirstInsensitive("hello", "Hello World");
+        assertEquals(0, index);
+    }
+
+    @Test
+    void testFindFirstInsensitiveNotMatch() {
+        int index = HorspoolSearch.findFirstInsensitive("helo", "Hello World");
+        assertEquals(-1, index);
+    }
+
+    @Test
+    void testGetLastComparisons() {
+        HorspoolSearch.findFirst("World", "Hello World");
+        int lastSearchNumber = HorspoolSearch.getLastComparisons();
+        assertEquals(7, lastSearchNumber);
+    }
+
+    @Test
+    void testGetLastComparisonsNotMatch() {
+        HorspoolSearch.findFirst("Word", "Hello World");
+        int lastSearchNumber = HorspoolSearch.getLastComparisons();
+        assertEquals(3, lastSearchNumber);
+    }
+
+    @Test
+    void testFindFirstPatternNull() {
+        assertThrows(NullPointerException.class,
+                () -> HorspoolSearch.findFirst(null, "Hello World"));
+    }
+
+    @Test
+    void testFindFirstTextNull() {
+        assertThrows(NullPointerException.class,
+                () -> HorspoolSearch.findFirst("Hello", null));
+    }
+}