update: 9/9/14 added the ng-learn link which has a flushed out example. If you are doing this you will need to change you test cases and include all the things like you were testing a directive.
If you want to set an input value to be invalid before submission then this is a good resource.
$scope.yourForm.nameOfElement.$setValidity( ‘reason’, false );
E.G.: You want to add an error to your start date in a search form.
$scope.searchForm.startDate.$setValidity( ‘date’, false );
To see a more fully explained example please see:
Click the launch demo button. Then click the script.js and the spec.js to see the full example.