How to spyOn a value property (rather than a method) with Jasmine

user_768722 0
Viewed 169401

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);
jasmine mocking unit-testing javascript
11 Answers

The best way is to use spyOnProperty. It expects 3 parameters and you need to pass get or set as a third param.

Example

const div = fixture.debugElement.query(By.css('.ellipsis-overflow'));
// now mock properties
spyOnProperty(div.nativeElement, 'clientWidth', 'get').and.returnValue(1400);
spyOnProperty(div.nativeElement, 'scrollWidth', 'get').and.returnValue(2400);

Here I am setting the get of clientWidth of div.nativeElement object.

user_5376470

The right way to do this is with the spy on property, it will allow you to simulate a property on an object with an specific value.

const spy = spyOnProperty(myObj, 'valueA').and.returnValue(1);
expect(myObj.valueA).toBe(1);
expect(spy).toHaveBeenCalled();
user_25636950

You can also use jasmin.creatSpyObj('ObjectName', [methodNames...], {prop1:propvalue, prop2:provalue2})

user_47543080
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