public void CopyToWorks()
{
var arr = Enumerable.Range(0, 10).ToArray();
var c = new FastCollection<int>();
c.CopyTo(arr, 0);
Assert.True(arr.SequenceEqual(Enumerable.Range(0, 10)));
c.Add(5);
c.CopyTo(arr, 0);
Assert.Equal(5, arr[0]);
Assert.True(arr.Skip(1).SequenceEqual(Enumerable.Range(1, 9)));
c.CopyTo(arr, 1);
Assert.Equal(5, arr[0]);
Assert.Equal(5, arr[1]);
Assert.True(arr.Skip(2).SequenceEqual(Enumerable.Range(2, 8)));
c.Add(6);
c.CopyTo(arr, 0);
Assert.Equal(5, arr[0]);
Assert.Equal(6, arr[1]);
Assert.True(arr.Skip(2).SequenceEqual(Enumerable.Range(2, 8)));
c.CopyTo(arr, 1);
Assert.Equal(5, arr[0]);
Assert.Equal(5, arr[1]);
Assert.Equal(6, arr[2]);
Assert.True(arr.Skip(3).SequenceEqual(Enumerable.Range(3, 7)));
}