public void SevenDayAvgTest()
        {
            WeightList wl = new WeightList(items);

            Assert.AreEqual(93.42857142, wl.SevenDayAvg(), 0.01);

            List <TodoItem> item1 = new List <TodoItem>(
                new TodoItem[] {
                new TodoItem(90, 4000, new DateTime(2019, 1, 1)),
                new TodoItem(92, 4000, new DateTime(2019, 1, 3)),
                new TodoItem(95, 4000, new DateTime(2019, 1, 6)),
                new TodoItem(96, 4000, new DateTime(2019, 1, 7)),
                // week
                new TodoItem(97, 4000, new DateTime(2019, 1, 8)),
                new TodoItem(99, 4000, new DateTime(2019, 1, 10)),
                new TodoItem(90, 4000, new DateTime(2019, 1, 11)),
                new TodoItem(90, 4000, new DateTime(2019, 1, 12)),
            });

            wl = new WeightList(item1);

            Assert.AreEqual(94.5, wl.SevenDayAvg(), 0.01);
        }