public async Task ThenItShouldReturnAOkResult()
        {
            //Arrange
            _statistics = new PaymentStatistics()
            {
                TotalNumberOfPayments = 13000,
                TotalNumberOfPaymentsWithRequiredPayment = 11000
            };
            _mediator.Setup(m => m.SendAsync(It.IsAny <GetPaymentsStatisticsRequest>()))
            .ReturnsAsync(new GetPaymentsStatisticsResponse()
            {
                IsValid = true,
                Result  = _statistics
            });

            // Act
            var actual = await _controller
                         .GetPaymentStatistics()
                         .ConfigureAwait(false);

            // Assert
            Assert.IsNotNull(actual);
            Assert.IsInstanceOf <OkNegotiatedContentResult <PaymentStatistics> >(actual);

            var paymentStatistics = ((OkNegotiatedContentResult <PaymentStatistics>)actual).Content;

            paymentStatistics.TotalNumberOfPayments.Should().Be(13000);
            paymentStatistics.TotalNumberOfPaymentsWithRequiredPayment.Should().Be(11000);
        }