public void ForProductByParameter_OneValue()
        {
            Number v1  = 2d;
            var    v1d = new Derivative1Value
            {
                First = 3
            };

            var d = DerivativeOperator.ForProductByParameter(
                productValues: new[] { v1 },
                valueDerivativeByParameter: new[] { v1d });

            d.First.AssertIsEqualTo(3d);
        }
        public void ForProductByParameter_TwoValues()
        {
            Number v1  = 2;
            var    v1d = new Derivative1Value
            {
                First = 3
            };

            Number v2  = 7;
            var    v2d = new Derivative1Value
            {
                First = 11
            };

            var d = DerivativeOperator.ForProductByParameter(
                productValues: new[] { v1, v2 },
                valueDerivativeByParameter: new[] { v1d, v2d });

            d.First.AssertIsEqualTo(3d * 7 + 2 * 11);
        }