observableBehaviors.js

/// <reference path="../src/observable.js" />

describe('Observable', {
    'Should be subscribable': function () {
        var instance = new ko.observable();
        value_of(ko.isSubscribable(instance)).should_be(true);
    },

    'Should advertise that instances are observable': function () {
        var instance = new ko.observable();
        value_of(ko.isObservable(instance)).should_be(true);
    },

    'Should be able to write values to it': function () {
        var instance = new ko.observable();
        instance(123);
    },

    'Should advertise that instances can have values written to them': function () {
        var instance = new ko.observable(function () { });
        value_of(ko.isWriteableObservable(instance)).should_be(true);
    },

    'Should be able to read back most recent value': function () {
        var instance = new ko.observable();
        instance(123);
        instance(234);
        value_of(instance()).should_be(234);
    },

    'Should initially have undefined value': function () {
        var instance = new ko.observable();
        value_of(instance()).should_be(undefined);
    },

    'Should be able to set initial value as constructor param': function () {
        var instance = new ko.observable('Hi!');
        value_of(instance()).should_be('Hi!');
    },

    'Should notify subscribers about each new value': function () {
        var instance = new ko.observable();
        var notifiedValues = [];
        instance.subscribe(function (value) {
            notifiedValues.push(value);
        });

        instance('A');
        instance('B');

        value_of(notifiedValues.length).should_be(2);
        value_of(notifiedValues[0]).should_be('A');
        value_of(notifiedValues[1]).should_be('B');
    },

    'Should be able to tell it that its value has mutated, at which point it notifies subscribers': function () {
        var instance = new ko.observable();
        var notifiedValues = [];
        instance.subscribe(function (value) {
            notifiedValues.push(value.childProperty);
        });

        var someUnderlyingObject = { childProperty : "A" };
        instance(someUnderlyingObject);
        value_of(notifiedValues.length).should_be(1);
        value_of(notifiedValues[0]).should_be("A");

        someUnderlyingObject.childProperty = "B";
        instance.valueHasMutated();
        value_of(notifiedValues.length).should_be(2);
        value_of(notifiedValues[1]).should_be("B");
    }
});