public void UpdateGstPriceTest()
        {
            var     controller  = new InvoiceController(messageProcessor);
            decimal setGstPrice = 14.5M;

            IActionResult actionResult   = controller.SetGstPrice(setGstPrice);
            var           responseUpdate = actionResult as ObjectResult;

            actionResult = controller.GetGstPrice();
            var responseSelect = actionResult as ObjectResult;

            Assert.AreEqual(responseUpdate.Value, true);
            Assert.AreEqual(responseSelect.Value, setGstPrice);
        }