public static async Task WriteNestedAsyncEnumerable <TElement>(IEnumerable <TElement> source, int delayInterval, int bufferSize)
        {
            JsonSerializerOptions options = new JsonSerializerOptions
            {
                DefaultBufferSize = bufferSize
            };

            string expectedJson = JsonSerializer.Serialize(new { Data = source });

            using var stream = new Utf8MemoryStream();
            var asyncEnumerable = new MockedAsyncEnumerable <TElement>(source, delayInterval);
            await JsonSerializer.SerializeAsync(stream, new { Data = asyncEnumerable }, options);

            JsonTestHelper.AssertJsonEqual(expectedJson, stream.ToString());
            Assert.Equal(1, asyncEnumerable.TotalCreatedEnumerators);
            Assert.Equal(1, asyncEnumerable.TotalDisposedEnumerators);
        }
        public static async Task WriteAsyncEnumerableOfAsyncEnumerables <TElement>(IEnumerable <TElement> source, int delayInterval, int bufferSize)
        {
            JsonSerializerOptions options = new JsonSerializerOptions
            {
                DefaultBufferSize = bufferSize
            };

            const int OuterEnumerableCount = 5;
            string    expectedJson         = JsonSerializer.Serialize(Enumerable.Repeat(source, OuterEnumerableCount));

            var innerAsyncEnumerable = new MockedAsyncEnumerable <TElement>(source, delayInterval);
            var outerAsyncEnumerable =
                new MockedAsyncEnumerable <IAsyncEnumerable <TElement> >(
                    Enumerable.Repeat(innerAsyncEnumerable, OuterEnumerableCount), delayInterval);

            using var stream = new Utf8MemoryStream();
            await JsonSerializer.SerializeAsync(stream, outerAsyncEnumerable, options);

            JsonTestHelper.AssertJsonEqual(expectedJson, stream.ToString());
            Assert.Equal(1, outerAsyncEnumerable.TotalCreatedEnumerators);
            Assert.Equal(1, outerAsyncEnumerable.TotalDisposedEnumerators);
            Assert.Equal(OuterEnumerableCount, innerAsyncEnumerable.TotalCreatedEnumerators);
            Assert.Equal(OuterEnumerableCount, innerAsyncEnumerable.TotalDisposedEnumerators);
        }