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

Question

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

Answer 1

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.