如何用Jasmine窥探一个value属性（而不是一个方法） [英] How to spyOn a value property (rather than a method) with Jasmine
问题描述
Jasmine的 spyOn 可以改变方法的行为，但有没有办法改变对象的值属性（而不是方法）？代码如下所示：
Jasmine's spyOn is good to change a method's behavior, but is there any way to change a value property (rather than a method) for an object? the code could be like below:
spyOn(myObj, 'valueA').andReturn(1);
expect(myObj.valueA).toBe(1);
推荐答案
2017年2月，他们合并了PR添加此功能，他们在2017年4月发布。
In February 2017, they merged a PR adding this feature, they released in April 2017.
所以要监视你使用的getter / setter：
const spy = spyOnProperty（myObj，' myGetterName'，'get'）;
其中myObj是您的实例，'myGetterName'是您在类中定义的名称 get myGetterName（）{ } ，第三个参数是类型获取或设置。
so to spy on getters/setters you use:
const spy = spyOnProperty(myObj, 'myGetterName', 'get');
where myObj is your instance, 'myGetterName' is the name of that one defined in your class as get myGetterName() {} and the third param is the type get or set.
您可以使用与已使用 spyOn 创建的间谍相同的断言。
You can use the same assertions that you already use with the spies created with spyOn.
所以你可以举例如：
const spy = spyOnProperty(myObj, 'myGetterName', 'get'); // to stub and return nothing. Just spy and stub.
const spy = spyOnProperty(myObj, 'myGetterName', 'get').and.returnValue(1); // to stub and return 1 or any value as needed.
const spy = spyOnProperty(myObj, 'myGetterName', 'get').and.callThrough(); // Call the real thing.
以下是github源代码中的行，如果您感兴趣，可以使用此方法。
Here's the line in the github source code where this method is available if you are interested.
用茉莉花回答原始问题2.6.1，你会：
Answering the original question, with jasmine 2.6.1, you would:
const spy = spyOnProperty(myObj, 'valueA', 'get').andReturn(1);
expect(myObj.valueA).toBe(1);
expect(spy).toHaveBeenCalled();
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