diff --git a/core/test/processing/data/SortTest.java b/core/test/processing/data/SortTest.java
new file mode 100644
index 0000000000..7dab624f68
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+++ b/core/test/processing/data/SortTest.java
@@ -0,0 +1,165 @@
+package processing.data;
+
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+/**
+ * Sort.java is an abstract class implementing quicksort with three abstract methods:
+ * 1. size() - returns the number of elements
+ * 2. compare(int a, int b) - compares elements at two indices
+ * 3. swap(int a, int b) - swaps elements at two indices
+ */
+public class SortTest {
+
+    /**
+     * Concrete implementation of Sort for testing using an int array.
+     */
+    private static class IntArraySort extends Sort {
+        int[] data;
+
+        IntArraySort(int[] data) {
+            this.data = data;
+        }
+
+        @Override
+        public int size() {
+            return data.length;
+        }
+
+        @Override
+        public int compare(int a, int b) {
+            return Integer.compare(data[a], data[b]);
+        }
+
+        @Override
+        public void swap(int a, int b) {
+            int temp = data[a];
+            data[a] = data[b];
+            data[b] = temp;
+        }
+    }
+
+    @Test
+    public void testSortAlreadySorted() {
+        int[] data = {1, 2, 3, 4, 5};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.run();
+        assertArrayEquals(new int[]{1, 2, 3, 4, 5}, data);
+    }
+
+    @Test
+    public void testSortReversed() {
+        int[] data = {5, 4, 3, 2, 1};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.run();
+        assertArrayEquals(new int[]{1, 2, 3, 4, 5}, data);
+    }
+
+    @Test
+    public void testSortUnsorted() {
+        int[] data = {3, 1, 4, 1, 5, 9, 2, 6};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.run();
+        assertArrayEquals(new int[]{1, 1, 2, 3, 4, 5, 6, 9}, data);
+    }
+
+    @Test
+    public void testSortSingleElement() {
+        int[] data = {42};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.run();
+        assertArrayEquals(new int[]{42}, data);
+    }
+
+    @Test
+    public void testSortEmptyArray() {
+        int[] data = {};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.run();
+        assertArrayEquals(new int[]{}, data);
+    }
+
+    @Test
+    public void testSortTwoElements() {
+        int[] data = {2, 1};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.run();
+        assertArrayEquals(new int[]{1, 2}, data);
+    }
+
+    @Test
+    public void testSortTwoElementsAlreadySorted() {
+        int[] data = {1, 2};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.run();
+        assertArrayEquals(new int[]{1, 2}, data);
+    }
+
+    @Test
+    public void testSortWithDuplicates() {
+        int[] data = {3, 3, 3, 3};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.run();
+        assertArrayEquals(new int[]{3, 3, 3, 3}, data);
+    }
+
+    @Test
+    public void testSortWithNegativeNumbers() {
+        int[] data = {0, -3, 5, -1, 2};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.run();
+        assertArrayEquals(new int[]{-3, -1, 0, 2, 5}, data);
+    }
+
+    @Test
+    public void testSortWithMixedDuplicatesAndNegatives() {
+        int[] data = {4, -2, 4, 0, -2};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.run();
+        assertArrayEquals(new int[]{-2, -2, 0, 4, 4}, data);
+    }
+
+    @Test
+    public void testSizeReflectsArrayLength() {
+        int[] data = {10, 20, 30};
+        IntArraySort sorter = new IntArraySort(data);
+        assertEquals(3, sorter.size());
+    }
+
+    @Test
+    public void testSwapExchangesElements() {
+        int[] data = {10, 20, 30};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.swap(0, 2);
+        assertArrayEquals(new int[]{30, 20, 10}, data);
+    }
+
+    @Test
+    public void testCompareReturnsNegativeWhenLess() {
+        int[] data = {1, 5};
+        IntArraySort sorter = new IntArraySort(data);
+        assertTrue(sorter.compare(0, 1) < 0);
+    }
+
+    @Test
+    public void testCompareReturnsPositiveWhenGreater() {
+        int[] data = {5, 1};
+        IntArraySort sorter = new IntArraySort(data);
+        assertTrue(sorter.compare(0, 1) > 0);
+    }
+
+    @Test
+    public void testCompareReturnsZeroWhenEqual() {
+        int[] data = {3, 3};
+        IntArraySort sorter = new IntArraySort(data);
+        assertEquals(0, sorter.compare(0, 1));
+    }
+
+    @Test
+    public void testSortDescendingLargeArray() {
+        int[] data = {6, 5, 4, 3, 2, 1};
+        IntArraySort sorter = new IntArraySort(data);
+        sorter.run();
+        assertArrayEquals(new int[]{1, 2, 3, 4, 5, 6}, data);
+    }
+}
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