// retoor <retoor@molodetz.nl>
import "html" for Document
var doc = Document.parse("<div><p>One</p><span>Two</span><a>Three</a></div>")
var span = doc.querySelector("span")
System.print(span.previousSibling != null) // expect: true
System.print(span.nextSibling != null) // expect: true
System.print(span.previousElementSibling.tagName) // expect: P
System.print(span.nextElementSibling.tagName) // expect: A
var p = doc.querySelector("p")
System.print(p.previousElementSibling == null) // expect: true
System.print(p.nextElementSibling.tagName) // expect: SPAN
var a = doc.querySelector("a")
System.print(a.previousElementSibling.tagName) // expect: SPAN
System.print(a.nextElementSibling == null) // expect: true