it("should collect errors from the child controls", () => {
        var one = new Control("one", validator("a", true));
        var two = new Control("one", validator("b", true));
        var g = new ControlGroup({"one": one, "two": two});

        expect(Validators.group(g)).toEqual({"a": [one], "b": [two]});
      });

 it("should collect errors from all the validators", () => {
   var c = Validators.compose([validator("a", true), validator("b", true)]);
   expect(c(new Control(""))).toEqual({
     "a": true,
     "b": true
   });
 });

 constructor(c:ControlDirective) {
   c.validator = Validators.compose([c.validator, Validators.required]);
 }

 () => { expect(Validators.required(new Control("not empty"))).toEqual(null); });