Add test case for negative rod length in RodCuttingTest

Author: Chiefpatwal

src/test/java/com/thealgorithms/dynamicprogramming/RodCuttingTest.java

@@ -93,4 +93,11 @@ void testCutRodEmptyPrices() {
         int length = 5;
         assertThrows(IllegalArgumentException.class, () -> RodCutting.cutRod(prices, length), "An empty prices array should throw an IllegalArgumentException.");
     }
+    @Test
+    void testCutRodNegativeLength() {
+        int[] prices = {1, 5, 8, 9, 10}; // Prices are irrelevant for negative length
+        int length = -1;
+        assertThrows(IllegalArgumentException.class, () -> RodCutting.cutRod(prices, length),
+                "A negative rod length should throw an IllegalArgumentException.");
+    }
 }