public void Prepend_should_apply_to_null() {
            DomDocument doc = new DomDocument();
            Assert.DoesNotThrow(() => doc.Prepend((DomNode) null));
            Assert.Same(doc, doc.Prepend((DomNode) null));

            Assert.DoesNotThrow(() => doc.Prepend((IEnumerable<DomNode>) null));
            Assert.Same(doc, doc.Prepend((IEnumerable<DomNode>) null));
        }