TypeError: Cannot read properties of undefined (reading 'activeIndex') - swiper v11; angular v18

[gugafreitas]

I'm encountering a TypeError: Cannot read properties of undefined (reading 'activeIndex') error in my Angular component unit test.
The issue arises when trying to access swiper.activeIndex in the component.
I think the problem is that i initialize a variable as a HTMLElement, and then it is not recognized as a swiper container.
Could the solution be to mock up the swiper? If so, how?