具有属性的 jasmine.createSpyObj

在我的 Angular 测试中模拟依赖项时，我通常使用以下命令创建一个间谍对象jasmine.createSpyObj:

const serviceSpy= jasmine.createSpyObj('MyService', ['method']);

然后将其提供给 TestBed：

  providers: [
    {provide: MyService, useValue: serviceSpy}
  ]

当我在测试中使用它时，我可以指定所需的返回值：

serviceSpy.method.and.returnValue(of([...]));

现在我还需要模拟属性，但我不知道应该如何完成。createSpyObj确实允许定义属性名称：

const serviceSpy= jasmine.createSpyObj('MyService', ['method'], ['property']);

但我根据大量文章和答案尝试了各种解决方案，但没有成功，例如：

// Cannot read property 'and' of undefined    
serviceSpy.property.and.returnValue(true);  
// not declared configurable
spyOnProperty(serviceSpy, 'property').and.returnValue(true);  
// no build errors, but value stays 'undefined'
serviceSpy.property = true;  

我能让它“一半”工作的唯一方法是：

let fakeValue = true;
const serviceSpy= jasmine.createSpyObj('MyService', ['method'], {'property': fakeValue});

这里的问题是它是在创建时一次性设置的。如果我想改变测试中的期望值，这是行不通的。

fakeValue = false;
serviceSpy.property ==> stays to the initial value 'true';

是否存在通过创建间谍对象来解决模拟方法和属性的解决方案，或者我应该创建自己的假类，然后可以在其上使用spyOn and spyOnProperty?

我还想知道属性数组的用法是什么createSpyObj定义。到目前为止，我还没有在网上看到任何解释它的例子。

Per 文档 https://jasmine.github.io/tutorials/spying_on_properties（强调我的）：

您可以通过以下方式快速创建具有多个属性的间谍对象 将属性数组或散列作为第三个参数传递给createSpyObj。在这种情况下，您将不会有对创建的引用 间谍，所以如果您稍后需要改变他们的间谍策略，您将 必须使用Object.getOwnPropertyDescriptor方法.

it("creates a spy object with properties", function() {
  let obj = createSpyObj("myObject", {}, { x: 3, y: 4 });
  expect(obj.x).toEqual(3);

  Object.getOwnPropertyDescriptor(obj, "x").get.and.returnValue(7);
  expect(obj.x).toEqual(7);
});

间谍属性是描述符（参见例如Object.defineProperty on MDN https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty），因此要访问间谍对象，您需要获取描述符对象，然后与get and set其上定义的方法。

在 TypeScript 中，编译器需要一些帮助。createSpyObj https://github.com/DefinitelyTyped/DefinitelyTyped/blob/d063d0175b3eb59a7a4cc5e64992f8a220d9a910/types/jasmine/index.d.ts#L292-L295返回any or SpyObj<T>, and a SpyObj只定义了methods被监视：

type SpyObj<T> = T & {
    [K in keyof T]: T[K] extends Func ? T[K] & Spy<T[K]> : T[K];
               // |     if it's a     |    spy on it     | otherwise leave
               // |     callable      |                  | it alone
};

所以要访问.and在描述符的 getter 上，你需要可选链接 https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#optional-chaining (as Object.getOwnPropertyDescriptor可能会回来undefined) and a 类型断言 https://www.typescriptlang.org/docs/handbook/basic-types.html#type-assertions to a Spy https://github.com/DefinitelyTyped/DefinitelyTyped/blob/d063d0175b3eb59a7a4cc5e64992f8a220d9a910/types/jasmine/index.d.ts#L959-L965:

(Object.getOwnPropertyDescriptor(obj, "x")?.get as Spy<() => number>).and.returnValue(7);

操场 https://www.typescriptlang.org/play?#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-VkXIe7FuOkBZOKIUnk84QVs4bIhQ8OhtZCC+C9ksgAJSwWWGloAgmgaCYBELxvBocQAD5sBAs5fOCu5PC0YCvO884CPykjRHwb7Dl+mA-no-6AcB4QANYgIQUDjJcEBQdws4GB0IzkZR1HzqiEDnAx87Xjwt5ZCE-Z7C+EBfvkhSuiAFzcXE6Ezpha4buicCYgiOJ7leyAPsep5IDhV43n0AkQNpT4vjhn7fr+hAAUBIHIWBkHQbOcJYoikLPA5qFyYQmEQNh5K4VZhE2cREQsVRnFOfRjFvBAEVsRxXEGDx0iKTaIChMpxLIFeABkJKBbOADSTHxRRkXnGhnElTxhl3n2A4iVxxU8QVYTSa1sk1a1gprm8OBoKMmAoJlADCpTADY4S9iM9XGUJKBxKwOG1AAVGtEAAEK+SgiyYGa7wbIsmU2EQczaqgk02BkM5RCw8zAMAFLgFS8qlHSHTjOKLTnftIR6GKEApH0V1PSeQSQJNLCZM+4ojMh5TQHsmXYBAoCysjmUoJNyqYPgph6DdEBrbUOH8lEAgwFAUAY3o8iBetm07ag+2HRox2ned8xLGDU36lAuxgPdF1PS94kIyd8RJCkaBjBsnS2Jzv2+TowR8xDpM4QaQuU9LyRmAz5JM9tu1s06R0-WdquXTjT03eOk69i4IuPc9lKFMrjtJH0nYQDKNh0nDUB8-rstMS2PAk2TgWOzYzuuM2rYCIkBtoPiEAGOODKDdNs0xEbZImyze0HRbHNW9ztvXRkT0AZOrv2GLHuS6jE4+-0ITOEEYt21N0fk3XE42HreEEURdnhFnQFfGYed6DEBerRtpus2XYHK9bF2833DtPY3zevZ7P0Gv0N7Dj9Sz2DY0Sw0E7e9J3-vBEHPfPbvA+x-vGdj9ZtkkRNJ6ABJPQowoAzQXkvRmK8S7mw3pXG2O8a5UCgK0L8o1+gH3dkfVuKwz58QvlLK+N9pzPm9o-P2YC5Y-RQa0F6GDIB90-uSWhYB0G+z1oA4AICwEQKgcbGBZt16WyllvHmyxd5qFNGgVoWDxZvRPsMHABCyCX0WNfW+2R74aA7pQlwytpF0KYVrQKhjhYZy4Tw8B+dC4QGLkI9mm8q5IPtrkWw4A5EoAxjIt+GwgIoFIhvKhQQVbMLJBgOk5iBAADcoD2CyLYk2uBAjENCd3H8ISbD7SelAHQqBPR6EypFchvsQgB1ft3LAe0mKxJxmAA4agwktEwNEkA9ddE2B2iUMoFQM6xPiYKBQA0zDDVGhASxoDrFzT4kZQSA5lrL02ucKWp9lGQFUUQ9RJDgkn1xiY8k7hVA+USSvP8YsSlP3KRDbuuyxb7LJHHAQ08c5zz4ScpZUsW4QGiaUJGkVbnPXufIwo3TygCDElSSSby5BCjkMMoaI1MphD-NkCBvF+JzL2AswK8TfYLFEEhFCGg1zQOZg48uTjEHLFhvqSayzjAJA0IsFgCDRbPVaE3Z6yERqkV8R-buCxgYJEgHFfCWQFgHA6JAN2EAWygA0FMDYIcfojXyKUDoXQei+0GMMRpQK+70sFkyvWHUbGLNXqXRxrLxGkLcRLUFjI+XXSVQYgc9ThhsuBSMTAv16D2FNIOH5PS9Ux3JC3B1ZAg3gpwVC-OGdTUL3eRauBIiuZUtteG35tgYa92dTcqWOw9jupGDKr5Z0-UBu+VmkIcUXAtjlkLJuUqXojROl3KWRl5Y-S+UG8oIRgDX3UE0zNPSR6jjUL22wAh-4RAhRJDKfC0gEmhaS5NwiK6iOcdS7ItKnq9kwORHN7883Ks3TbMWcqQAKpwC6q2CQCYDohoW-Yuqml933eRMgow9ACFmvGogK6BFLItFys9Lqvk+tcvWT6ETabRPgaermFb7AQ0nXME6Iw3ixPIjkYdtg4MgHOFASNpQOKYmgyeOdehY0L3-REM1q7zggcpeBnBISoPX0yhgFQ+wjo2srsh1DWb0Ogyw1AHDIacLcdUAAdW1CR4AZHFScayF+HjYAaNLqyvRxN5rYHrpYzamlSxjA6AAKKARcEevmXdEOhJlSZ3JTjBPPknZJwKjnzOWdcFQGwGhPJEtohACzxh04EiTTJjDIS+4bxeFMDQvlr4mVfsEn11sWVSxcPYLUeh1WtF1DADeKR9rwf0TjEYKQvUQzRhhepvRt7bpyPlvUTTmsmqIIM9cGVM7KaDlRmj6LZmNSxXpQKs1BsNTICOMcw8fILiXHEcjnGAAy9hyLhDeKMCU5wvw2ASMAMAaRmq7f25AFOIBWloHSqYHrhoVNqdUAN+amKX0L1G+Scbz3hzTYyLN6cc5FyxFuxR1b63dikUBvoI7vh-v+XiBdw23ZuvAmwKXD0bTh58KHJ9mZk3x2PKYltuWBgFuw5h-RUqcUEqZ2qgYWqQW-w2EIFQL4rwUAo7AHtMw4R+RxHYHDwpl3+pnwRWMxnzPWf2HZ6jk6aALgOuxeSYIEvwBs453tNw4o0ACHOA6lgKAEitENEx1oc9o34T-mFcIY1DfOCoGZgAjgkUo+KTeDS09TWmWB6Y4VrDYeshSiO4C8hoXwetQLvE6z2G3Rv7dO5dxYN3EpkBfvsDIsAPkWB0lPlkHypPPd0yC-0hJQyRejKRQBnHGLhuDmQItRX75x0yhnlOZ5s8ZF8J-jGhdZrybZAJCirIgGyS7wEFw+e-CyTiPrmOmbk4BDq-2ujmfnfl1mqFEAA