javascript 如何在 Jest 中测试类构造函数
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How to test class constructor in Jest
提问by Le garcon
Let's say I have a class like following:
假设我有一个如下所示的课程：
class SomeClass {
constructor(a, b) {
this.a = a;
this.b = b;
}
}
How can I test through Jest that constructor was initialized the right way? Say... this.a = aand this.b = band not vice versa?
如何通过 Jest 测试构造函数是否以正确的方式初始化？说...this.a = a而this.b = b不是反之亦然？
I know that I can execute toBeCalledWithbut that won't let me check the constructor's logic. I was also thinking about making mockImplementationbut in this case it seems pointless as I will rewrite the logic, or I may not be aware of all the nuances of creating mocks
我知道我可以执行，toBeCalledWith但这不会让我检查构造函数的逻辑。我也在考虑制作，mockImplementation但在这种情况下似乎毫无意义，因为我将重写逻辑，或者我可能不知道创建模拟的所有细微差别
回答by samanime
Just create an instance of the object and check it directly. Since it sets them on this, they are essentially public values:
只需创建对象的实例并直接检查它。由于它将它们设置为this，因此它们本质上是公共值：
it('works', () => {
const obj = new SomeClass(1, 2);
expect(obj.a).toBe(1);
expect(obj.b).toBe(2);
});
回答by Liviath
You can simply check the instance properties after initializing the class. Basicly the same as you can test the side effects of any function.
您可以在初始化类后简单地检查实例属性。基本上一样可以测试任何函数的副作用。
const a = Symbol();
const b = Symbol();
const classInstance = new SomeClass(a, b);
expect(classInstance.a).toBe(a);
expect(classInstance.b).toBe(b);
