淘汰赛计算似乎没有更新

Question

我有一个简单的视图模型，我正在对其进行单元测试，但我似乎无法理解这种行为。我认为这可能与淘汰赛有选择地跟踪依赖项或缓存计算结果有关。

代码（represented in this fiddle）：

function viewModel() {
 var serviceErrors = ko.observable([]),
     isCancelImmediately = ko.observable(true),
     futureDate = ko.observable(),
     errors = ko.computed(function() {
         var allErrors = serviceErrors(),
             isImmediate = isCancelImmediately(),
             selectedDate = futureDate();

         if(!selectedDate && !isImmediate) {
          allErrors.push('Please select a date if not immediate.');   
         }

         return allErrors;
     });

    return {
        futureDate: futureDate,
        errors: errors,
        isCancelImmediately: isCancelImmediately
    };
}
test('should give error if user has not selected a date when closing immediately', function() { 
    var sut = viewModel();

    ok(!sut.futureDate(), 'no date should be set to start with');    
    sut.isCancelImmediately(false);
    equal(sut.errors().length, 1, 'should contain a future date error if user hasn\'t entered a date');
    sut.futureDate('11/12/2014');
    equal(sut.futureDate(), '11/12/2014', 'should have set future date');
    equal(sut.errors().length, 0, 'should not be showing error');
});

谁能告诉我为什么最后一个断言失败了？

Answer 1

我认为：

allErrors.push('Please select a date if not immediate.'); 

实际上是将一个字符串推送到您的 serviceErrors observable 包含的数组中。因此，当您在 addErrors 上运行 push 时，您也会推送到 serviceErrors。