How to set scope property with ng-init?

You are trying to read the set value before Angular is done assigning.

Demo:

var testController = function ($scope, $timeout) {
    console.log('test');
    $timeout(function(){
        console.log($scope.testInput);
    },1000);
}

Ideally you should use $watch as suggested by @Beterraba to get rid of the timer:

var testController = function ($scope) {
    console.log('test');
    $scope.$watch("testInput", function(){
        console.log($scope.testInput);
    });
}