public void GroupByExpressionHours() { var sw = Stopwatch.StartNew(); INullableQuerySerie <float> nullableQuerySerie = _unitUnderTest9m.GroupBy("3h", a => a.First()); IReadOnlyList <ISingleDataRow <float?> > result = nullableQuerySerie.Rows; IObjectQuerySerie result2 = nullableQuerySerie; object val = result2.Rows.First().Value; result[0].TimeUtc.Should().Be(new DateTime(2010, 1, 1, 12, 0, 0, DateTimeKind.Utc)); result[1].TimeUtc.Should().Be(new DateTime(2010, 1, 1, 15, 0, 0, DateTimeKind.Utc)); sw.Stop(); }