Add unit tests for Search2DMatrix implementations

- Added JUnit tests covering both variations of 2D matrix search.
- Tests validate correctness for typical inputs and edge cases.
- Helps increase code coverage and ensures algorithm correctness.

Author: MohakAgrawal25

src/test/java/com/thealgorithms/matrix/Search2DMatrixTest.java

@@ -0,0 +1,30 @@
+package com.thealgorithms.matrix;
+
+import static org.junit.jupiter.api.Assertions.*;
+import org.junit.jupiter.api.Test;
+
+public class Search2DMatrixTest {
+
+    @Test
+    public void testSearchMatrixSortedRowsAndCols() {
+        int[][] matrix = {
+            {1, 4, 7, 11},
+            {2, 5, 8, 12},
+            {3, 6, 9, 16},
+            {10, 13, 14, 17}
+        };
+        assertTrue(Search2DMatrix.searchMatrixSortedRowsAndCols(matrix, 5));
+        assertFalse(Search2DMatrix.searchMatrixSortedRowsAndCols(matrix, 20));
+    }
+
+    @Test
+    public void testSearchMatrixFlattenedSorted() {
+        int[][] matrix = {
+            {1, 3, 5, 7},
+            {10, 11, 16, 20},
+            {23, 30, 34, 50}
+        };
+        assertTrue(Search2DMatrix.searchMatrixFlattenedSorted(matrix, 3));
+        assertFalse(Search2DMatrix.searchMatrixFlattenedSorted(matrix, 4));
+    }
+}