public async Task UpdateDiscountSuccessfully()
{
//Arrange
var expectedCoupon = this.DesiredDiscount;
_mockDiscountRepository.Setup(x => x.UpdateDiscount(It.IsAny <Coupon>())).ReturnsAsync(true);
//Act
var result = await _sut.UpdateDiscount(expectedCoupon);
//Assert
Assert.NotNull(result);
var response = Assert.IsType <ActionResult <bool> >(result);
var okResult = response.Result as OkObjectResult;
Assert.True(Convert.ToBoolean(okResult.Value));
}