public void Test_Head()
{
var writer = new SliceWriter(64);
var slice = writer.Head(0);
Assert.That(slice.Count, Is.EqualTo(0));
Assert.That(slice.Offset, Is.EqualTo(0));
//note: slice.Array is not guaranteed to be equal to writer.Buffer
Assert.That(() => writer.Head(1), Throws.InstanceOf <ArgumentOutOfRangeException>());
writer.WriteBytes(Slice.FromString("hello world!"));
slice = writer.Head(5);
Assert.That(slice.Array, Is.SameAs(writer.Buffer));
Assert.That(slice.Offset, Is.EqualTo(0));
Assert.That(slice.Count, Is.EqualTo(5));
Assert.That(slice.ToStringAscii(), Is.EqualTo("hello"));
slice = writer.Head(12);
Assert.That(slice.Array, Is.SameAs(writer.Buffer));
Assert.That(slice.Offset, Is.EqualTo(0));
Assert.That(slice.Count, Is.EqualTo(12));
Assert.That(slice.ToStringAscii(), Is.EqualTo("hello world!"));
Assert.That(() => writer.Head(13), Throws.InstanceOf <ArgumentOutOfRangeException>());
Assert.That(() => writer.Head(-1), Throws.InstanceOf <ArgumentOutOfRangeException>());
writer.WriteBytes(Slice.FromString("foo"));
slice = writer.Head(3);
Assert.That(slice.Array, Is.SameAs(writer.Buffer));
Assert.That(slice.Offset, Is.EqualTo(0));
Assert.That(slice.Count, Is.EqualTo(3));
Assert.That(slice.ToStringAscii(), Is.EqualTo("hel"));
slice = writer.Head(15);
Assert.That(slice.Array, Is.SameAs(writer.Buffer));
Assert.That(slice.Offset, Is.EqualTo(0));
Assert.That(slice.Count, Is.EqualTo(15));
Assert.That(slice.ToStringAscii(), Is.EqualTo("hello world!foo"));
Assert.That(() => writer.Head(16), Throws.InstanceOf <ArgumentOutOfRangeException>());
}