public async Task TestGetAppointmentOfClientByAppointmentId_Returns_ActionResult(string c, string a, bool r)
        {
            // Arrange
            var clientId      = new Guid(c);
            var appointmentId = new Guid(a);

            // Act
            var response = await controller.GetAppointmentForClientAsync(clientId, appointmentId);

            var result = response.Result;

            // Assert
            if (r)
            {
                result.Should().BeOfType <OkObjectResult>();
            }
            else
            {
                result.Should().BeOfType <NotFoundResult>();
            }
        }