Create QuickSortWhiteBoxTest.Java

src/test/java/com/github/pedrovgs/problem80/QuickSortWhiteBoxTest.java

@@ -0,0 +1,76 @@
+package com.github.pedrovgs.problem80;
+
+import junit.framework.TestCase;
+import org.junit.Before;
+import org.junit.Test;
+import java.lang.reflect.Method;
+
+import static org.junit.Assert.assertArrayEquals;
+
+public class QuickSortWhiteBoxTest extends TestCase {
+    private QuickSort quickSort;
+
+    @Before
+    public void setUp() {
+        quickSort = new QuickSort();
+    }
+
+    // Helper method to access private method in QuickSort Class
+    private Object invokePrivateMethod(String methodName, Class<?>[] parameterTypes, Object[] parameters) throws Exception {
+        Method method = QuickSort.class.getDeclaredMethod(methodName, parameterTypes);
+        method.setAccessible(true);
+        return method.invoke(quickSort, parameters);
+    }
+
+    // Test sort method with valid input to cover validateInput, quickSort, partition, and swap
+    @Test
+    public void testSortValidInput() {
+        int[] numbers = {3, 6, 8, 10, 1, 2, 1};
+        quickSort.sort(numbers);
+        assertArrayEquals(new int[]{1, 1, 2, 3, 6, 8, 10}, numbers);
+    }
+
+    // Test validateInput with null input to cover the exception branch
+    @Test
+    public void testValidateInputNull() {
+        try {
+            quickSort.sort(null);
+            fail("Expected IllegalArgumentException");
+        } catch (IllegalArgumentException e) {
+            // Test passes
+        }
+    }
+
+    // Test partition method to ensure the pivoting logic works
+    @Test
+    public void testPartition() throws Exception {
+        int[] numbers = {3, 6, 8, 10, 1, 2, 1};
+        int pivotIndex = (int) invokePrivateMethod("partition", new Class[]{int[].class, int.class, int.class}, new Object[]{numbers, 0, numbers.length - 1});
+
+        assertTrue(pivotIndex >= 0 && pivotIndex < numbers.length);
+
+        for (int i = 0; i < pivotIndex; i++) {
+            assertTrue(numbers[i] <= numbers[pivotIndex]);
+        }
+        for (int i = pivotIndex + 1; i < numbers.length; i++) {
+            assertTrue(numbers[i] > numbers[pivotIndex]);
+        }
+    }
+
+    // Test quickSort with left < right branch
+    @Test
+    public void testQuickSortBranch() throws Exception {
+        int[] numbers = {3, 6, 8, 10, 1, 2, 1};
+        invokePrivateMethod("quickSort", new Class[]{int[].class, int.class, int.class}, new Object[]{numbers, 0, numbers.length - 1});
+        assertArrayEquals(new int[]{1, 1, 2, 3, 6, 8, 10}, numbers);
+    }
+
+    // Testing quickSort method will return unsorted if array has single element
+    @Test
+    public void testQuickSortNotCalledIfArrayHasSingleElement() {
+        int[] numbers = {999};
+        quickSort.sort(numbers);
+        assertArrayEquals(new int[]{999}, numbers);
+    }
+
+}