Fixed Test

Author: sgindeed

src/test/java/com/thealgorithms/divideandconquer/DeterministicQuickSelectTest.java

@@ -1,27 +1,49 @@
 package com.thealgorithms.divideandconquer;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.*;
 
 import org.junit.jupiter.api.Test;
 
 class DeterministicQuickSelectTest {
 
     @Test
-    void testSelectKthSmallest() {
+    void testSelectKthSmallestBasic() {
         int[] arr = {7, 10, 4, 3, 20, 15};
-        assertEquals(3, DeterministicQuickSelect.select(arr, 1));
-        assertEquals(4, DeterministicQuickSelect.select(arr, 2));
-        assertEquals(7, DeterministicQuickSelect.select(arr, 3));
-        assertEquals(10, DeterministicQuickSelect.select(arr, 4));
-        assertEquals(15, DeterministicQuickSelect.select(arr, 5));
-        assertEquals(20, DeterministicQuickSelect.select(arr, 6));
+        assertEquals(3, DeterministicQuickSelect.select(arr.clone(), 1)); // smallest
+        assertEquals(4, DeterministicQuickSelect.select(arr.clone(), 2));
+        assertEquals(7, DeterministicQuickSelect.select(arr.clone(), 3));
+        assertEquals(10, DeterministicQuickSelect.select(arr.clone(), 4));
+        assertEquals(15, DeterministicQuickSelect.select(arr.clone(), 5));
+        assertEquals(20, DeterministicQuickSelect.select(arr.clone(), 6)); // largest
     }
 
     @Test
-    void testInvalidInput() {
-        assertThrows(IllegalArgumentException.class, () -> DeterministicQuickSelect.select(null, 1));
-        assertThrows(IllegalArgumentException.class, () -> DeterministicQuickSelect.select(new int[] {1, 2}, 0));
-        assertThrows(IllegalArgumentException.class, () -> DeterministicQuickSelect.select(new int[] {1, 2}, 3));
+    void testSelectSingleElement() {
+        int[] arr = {42};
+        assertEquals(42, DeterministicQuickSelect.select(arr, 1));
+    }
+
+    @Test
+    void testSelectWithDuplicates() {
+        int[] arr = {5, 3, 8, 5, 2, 3};
+        assertEquals(2, DeterministicQuickSelect.select(arr.clone(), 1));
+        assertEquals(3, DeterministicQuickSelect.select(arr.clone(), 2));
+        assertEquals(3, DeterministicQuickSelect.select(arr.clone(), 3));
+        assertEquals(5, DeterministicQuickSelect.select(arr.clone(), 4));
+        assertEquals(5, DeterministicQuickSelect.select(arr.clone(), 5));
+        assertEquals(8, DeterministicQuickSelect.select(arr.clone(), 6));
+    }
+
+    @Test
+    void testSelectEmptyArray() {
+        int[] arr = {};
+        assertThrows(IllegalArgumentException.class, () -> DeterministicQuickSelect.select(arr, 1));
+    }
+
+    @Test
+    void testSelectInvalidK() {
+        int[] arr = {1, 2, 3};
+        assertThrows(IllegalArgumentException.class, () -> DeterministicQuickSelect.select(arr, 0)); // k < 1
+        assertThrows(IllegalArgumentException.class, () -> DeterministicQuickSelect.select(arr, 4)); // k > length
     }
 }