added test for 3 multiplicators for simplify_product_function

src/test/py/test_read_math_function.py

@@ -91,6 +91,9 @@ class ReadFunction(unittest.TestCase):
     def test_simplify_product_function_2_multiplicators(self):
         self.assertEqual(simplify_product_function("p", "x*x"), ["x^2"])
 
+    def test_simplify_product_function_3_multiplicators(self):
+        self.assertEqual(simplify_product_function("p", "x*x*x"), ["x^3"])
+
 
 if __name__ == '__main__':
     unittest.main()