Refactor matrix initialization for test cases

Author: Dsannue

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

@@ -0,0 +1,26 @@
+package com.thealgorithms.matrix;
+
+import static org.junit.jupiter.api.Assertions.*;
+import org.junit.jupiter.api.Test;
+
+class StochasticMatrixTest {
+
+    @Test
+    void testRowStochasticMatrix() {
+        double[][] matrix = {{0.2, 0.5, 0.3},{0.1, 0.6, 0.3}};
+        assertTrue(StochasticMatrix.isRowStochastic(matrix));
+        assertFalse(StochasticMatrix.isColumnStochastic(matrix));
+    }
+
+    @Test
+    void testColumnStochasticMatrix() {
+        double[][] matrix = {{0.4, 0.2},{0.6, 0.8}};
+        assertTrue(StochasticMatrix.isColumnStochastic(matrix));
+    }
+
+    @Test
+    void testInvalidMatrix() {
+        double[][] matrix = {{0.5, -0.5},{0.5, 1.5}};
+        assertFalse(StochasticMatrix.isRowStochastic(matrix));
+    }
+}