Karma testing: TypeError: Attempted to assign to readonly property

Question

When I am trying to unit test my controller I am getting the error.When I debug the testcase's expect I am getting the expected value but its failing with below error.What am I missing here or whether I am testing the controller variable in a wrong manner?

My spec file is below

'use strict';
describe('Information.controller', function () {
beforeEach(angular.mock.module('asp'));
var InformationController, scope;

beforeEach(inject(function($controller, $rootScope) {
    scope = $rootScope.$new();
    InformationController = $controller('InformationController', {
        $scope: scope
    });
}));

fit('Should remove the object without info from the  object', function () {
    InformationController.Data = [
        {
            "ban": "03745645455",
            "accountNo": "0000drgyt456456565",
            "id": "2c4cc5e8-f360367"
        },
        {
            "ban": "27346fgh9080",
            "accountNo": "000456456ytr655680",
            "id": "2c4cc8ae-50bbf360367"
        }
    ];
    InformationController.banList = InformationController.Data.map((value, index) => (value && value.ban ? {'id': index, 'text': value.ban} : null))
    .filter(value => value);
    expect(InformationController.banList.length).toBe(3);
});
});

Answer 1

readonly error is caused by scope.page(in my InformationController) being undefined and then the code is trying to assign a property to undefined.Hence the modified beforeEach block as below

beforeEach(inject(function ($controller, $rootScope) {
        scope = $rootScope.$new();
        scope.page3 = {};
        InformationController = $controller('InformationController', {
            $scope: scope
        });
    }));

This solved the issue.