public void TestAppendMany()
        {
            PrimitiveColumn <int> intColumn = new PrimitiveColumn <int>("Int1");

            intColumn.AppendMany(null, 5);
            Assert.Equal(5, intColumn.NullCount);
            Assert.Equal(5, intColumn.Length);
            for (int i = 0; i < intColumn.Length; i++)
            {
                Assert.False(intColumn.IsValid(i));
            }

            intColumn.AppendMany(5, 5);
            Assert.Equal(5, intColumn.NullCount);
            Assert.Equal(10, intColumn.Length);
            for (int i = 5; i < intColumn.Length; i++)
            {
                Assert.True(intColumn.IsValid(i));
            }

            intColumn[2] = 10;
            Assert.Equal(4, intColumn.NullCount);
            Assert.True(intColumn.IsValid(2));

            intColumn[7] = null;
            Assert.Equal(5, intColumn.NullCount);
            Assert.False(intColumn.IsValid(7));
        }
        public void TestValidity()
        {
            PrimitiveColumn <int> dataFrameColumn1 = new PrimitiveColumn <int>("Int1", Enumerable.Range(0, 10).Select(x => x));

            dataFrameColumn1.Append(null);
            Assert.False(dataFrameColumn1.IsValid(10));
            for (long i = 0; i < dataFrameColumn1.Length - 1; i++)
            {
                Assert.True(dataFrameColumn1.IsValid(i));
            }
        }