Class which simplifies bootstraping of angular for unit tests.

Simply inject TestBed into the test, then use compile to match directives against the view.

class TestBed {
 final Injector injector;
 final Scope rootScope;
 final Compiler compiler;
 final Parser parser;


 Element rootElement;
 List<Node> rootElements;
 Block rootBlock;

 TestBed(
     Injector this.injector,
     Scope this.rootScope,
     Compiler this.compiler,
     Parser this.parser);


 /**
  * Use to compile HTML and activete its directives.
  *
  * If [html] parametr is:
  *
  *   - [String] then treat it as HTML
  *   - [Node] then treat it as the root node
  *   - [List<Node>] then treat it as a collection of nodse
  *
  * After the compilation the [rootElements] contains an array of compiled root nodes,
  * and [rootElement] contains the first element from the [rootElemets].
  *
  */
 Element compile(html) {
   if (html is String) {
     rootElements = toNodeList(html);
   } else if (html is Node) {
     rootElements = [html];
   } else if (html is List<Node>) {
     rootElements = html;
   } else {
     throw 'Expecting: String, Node, or List<Node> got $html.';
   }
   rootElement = rootElements[0];
   rootBlock = compiler(rootElements)(injector, rootElements);
   return rootElement;
 }

 /**
  * Convert an [html] String to a [List] of [Element]s.
  */
 List<Element> toNodeList(html) {
   var div = new DivElement();
   div.setInnerHtml(html, treeSanitizer: new NullTreeSanitizer());
   var nodes = [];
   for(var node in div.nodes) {
     nodes.add(node);
   }
   return nodes;
 }

 /**
  * Triggern a specific DOM element on a given node to test directives
  * which listen to events.
  */
 triggerEvent(element, name, [type='MouseEvent']) {
   element.dispatchEvent(new Event.eventType(type, name));
 }

 /**
  * Select an [OPTION] in a [SELECT] with a given name and trigger the
  * appropriate DOM event. Used when testing [SELECT] controlls in forms.
  */
 selectOption(element, text) {
   element.queryAll('option').forEach((o) => o.selected = o.text == text);
   triggerEvent(element, 'change');
 }
}