单元测试Angularjs指令，包含使用Jasmine的私有超时 [英] Unit Test Angularjs directive, which contains private timeout, with Jasmine

问题描述

我有一个指令，其行为应该有所不同，具体取决于自初始化以来经过的时间：

I have a directive, which should behave differently, depending on how much time passed since it's initialization:

am.directive('showText', () => ({
  restrict: 'E',
  replace: true,
  scope: {
    value: '@'
  },
  controller: ($scope, $timeout) => {
    console.log('timeout triggered');

    $scope.textVisible = false;

    let visibilityCheckTimeout = $timeout(() => {
      if (parseInt($scope.value, 10) < 100) {
        $scope.textVisible = true;
      }
    }, 330);

    // Clear timeout upon directive destruction
    $scope.$on('$destroy', $timeout.cancel(visibilityCheckTimeout));
  },
}));

问题是，当我尝试用Jasmine测试它时，我似乎无法忍受找到一种以任何方式触发此超时的方法。已经尝试了 $ timeout.flush（）和 $ timeout.verifyNoPendingTasks（）（实际上会抛出错误，如果我会评论 flush call）。但它仍然没有触发超时的回调执行

The problem is, that when I'm trying to test it with Jasmine, I can't seem to find a way to trigger this timeout in any way. Already tried a $timeout.flush() and $timeout.verifyNoPendingTasks() (which actually throws an error, if I'll comment flush call). But it's still not triggering that timeout's callback execution

describe('showText.', () => {
  let $compile;
  let $rootScope;
  let $scope;
  let $timeout;

  const compileElement = (rootScope, value = 0) => {
    $scope = rootScope.$new();
    $scope.value = value;

    const element = $compile(`
      <show-text
        value="value"
      ></show-text>
    `)($scope);

    $scope.$digest();

    return element;
  };

  beforeEach(() => {
    module('app.directives.showText');

    inject((_$compile_, _$rootScope_, _$timeout_) => {
      $compile = _$compile_;
      $rootScope = _$rootScope_;
      $timeout = _$timeout_;
    });
  });

  it(`Process lasts > 0.33s. Should show text.`, () => {
    const VALUE = 30;
    const element = compileElement($rootScope, VALUE);
    const elementContent = element.find('.show-text__content');

    $timeout.flush(1000);

    $timeout.verifyNoPendingTasks();

    $rootScope.$digest();

    expect(element.isolateScope().textVisible).toBeTruthy();
    expect(elementContent.length).toEqual(1);
    expect(elementContent.text().trim()).toBe('Example text');
  });
});

测试失败。

不能找到我做错了什么。关于如何正确测试这种情况的任何提示？

Can't find what am I doing wrong. Any tips on how to properly test such a case?

谢谢。

UPD
经过一些调查，我发现在这个特定的测试用例中，在 compileElement 函数中， value 属性未被 $ compile 服务评估。并等于value。我已经使用了相同的功能10次，并且无法获得，为什么它没有采用之前的 $ scope.value 的属性。

UPD After some investigation, I've found that in this particular test-case, in compileElement function, value property isn't being evaluated by $compile service. And equals "value". I've used same function already 10th of times, and can't get, why it's not taking a $scope.value's property as it was before.

推荐答案

发生这种情况的原因是 $ timeout.cancel（visibilityCheckTimeout）启动无条件地立即。相反，它应该是

The reason why this happens is that $timeout.cancel(visibilityCheckTimeout) launches unconditionally and immediately. Instead, it should be

$scope.$on('$destroy', () => $timeout.cancel(visibilityCheckTimeout));

可以采取一些措施来提高可测试性（除了之外） $ timeout 在这里作为一次性范围观察者工作并要求替换为一个）。

There are things that can be done to improve testability (besides the fact that $timeout works here as one-time scope watcher and asks to be replaced with the one).

$ timeout 可以成功间谍：

beforeEach(module('app', ($provide) => {
  $provide.decorator('$timeout', ($delegate) => {
    var timeoutSpy = jasmine.createSpy().and.returnValue($delegate);
    angular.extend(timeoutSpy, $delegate);
    spyOn(timeoutSpy, 'cancel').and.callThrough();
    return timeoutSpy;
  });
}));

私有 $ timeout 回调可以暴露给范围。

Private $timeout callback can be exposed to scope.

$scope._visibilityCheckHandler = () => {
  if (parseInt($scope.value, 10) < 100) {
    $scope.textVisible = true;
  }
};
$timeout($scope._visibilityCheckHandler, 330);

通过这种方式可以窥探所有电话并获得全面保障：

This way all of the calls can be spied and get full coverage:

let directiveScope;
...

const element = $compile(`...`)($scope);

directiveScope = element.isolateScope();
spyOn(directiveScope, '_visibilityCheckHandler').and.callThrough();

$scope.$digest();
...

expect($timeout).toHaveBeenCalledWith(directiveScope._visibilityCheckHandler, 330);
expect($timeout.cancel).not.toHaveBeenCalled();

在这种情况下，这里不需要为'> = 0.33s'和'<提供单独的规格。 0.33s'与 flush 延迟参数， $ timeout 已经在Angular规范中测试了内部工作。此外，回调逻辑可以单独测试 $ timeout spec。

In this case here's no need to have separate specs for '>= 0.33s' and '< 0.33s' with flush delay argument, $timeout's inner work was already tested in Angular specs. Also, callback logic can be tested separately from $timeout spec.

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