public async void DelayResult_TimeSpanSet_ReturnsDelayedResult()
        {
            // ARRANGE
            TimeSpan  timespan       = TimeSpan.FromSeconds(2);
            const int ExpectedResult = 100;

            // ACT
            var result = await TaskDelayAndRetry.DelayResult(result : ExpectedResult, delay : timespan);

            // ASSERT
            Assert.AreEqual(ExpectedResult, result);
        }
        public async void DownloadStringWithRetries_UriSet_ReturnsFetchedUriString()
        {
            // ARRANGE
            // - nothing to arrange

            // ACT
            var result = await TaskDelayAndRetry.DownloadStringWithRetries(uri : "http://stephencleary.com/");

            // ASSERT
            Assert.NotNull(result, "result is null.");

            var index = result.IndexOf(
                "http://stephencleary.com",
                0,
                result.Length,
                StringComparison.OrdinalIgnoreCase);

            Assert.AreNotEqual(-1, index, "index has unexpected value.");
        }