Unit testing an angularjs controller with a form in it - angularjs

Question

I'm trying to unit test a connection forms controller with karma and jasmine, but on thing I can't get to grips with.
The controller:
.controller('connectionController', ['$scope', '$rootScope', '$state', '$stateParams', '$http', '$localStorage',
function($scope, $rootScope, $state, $stateParams, $http, $localStorage){
$scope.userCredentials = {};
$scope.connectionError = false;
$scope.connectUser=function(){
if ($scope.connectionForm.$valid) {
//Do the login stuff here
//IF good --> state.go...
}
else {
console.log('Invalide.');
$scope.connectionError = true;
}
}
}])
Then in my HTML (simplified to a maximum):
<form name="connectionForm" novalidate>
<div class="form-group input-group" show-errors='{ showSuccess: true }'>
<span for="login" class="input-group-addon"></span>
<input type="text" ng-model="userCredentials.login" required>
</div>
<div class="form-group input-group" show-errors='{ showSuccess: true }'>
<span for="password" class="input-group-addon"></span>
<input type="password" ng-model="userCredentials.password" required>
</div>
<button class="btn btn-primary" ng-click="connectUser()">Connect</button>
</form>
And finally the test (specific 'it' that doesn't pass):
it('should connect user', function(){
scope.userCredentials.login = 'aUser';
scope.userCredentials.password = 'aPassword';
$httpBackend.when('POST', 'http://localhost:4711/api/token').
respond({ token: 'xxx', user: aUser });
scope.connectUser();
$httpBackend.flush();
});
So the the problem I get is that this:
TypeError: Cannot read property '$valid' of undefined
at Scope.$scope.connectUser (connection.js)
at null.<anonymous> (connection.js)
Si I think the basic problem comes from the fact that the controller doesn't have the access to stuff defined only on the html (like connectionForm...) and cannot get their properties.
Another thing to notice is that I do a state.go(..) when the connection was successful, could it be this ?
What can I do ? Or more, what am I doing wrong ?