How do you test new UI widgets?

This thread is more of a "show me what you got" style discussion starter than an actual question. https://curated.onl/nba-reddit/

Tell me how you test a brand new UI widget that you just created! It can be anything as long as it is a self-contained, single main purpose unit, UI control, widget, or call it whatever you want. You can go into detail about how you solve the initial idea (do you just write code, or use XML as well? Databinding? Common base class https://reversephonelookup.onl/for all your custom controls in a project, or just inherit from View (or an appropriate ViewGroup implementation)?), but the main idea is how you do manual UI/behaviour tests - do you create a new sandbox project, do you test it in your app in a new fragment/view, or just replace an existing view's content, or rather, add the control to it? Do you write unit tests for your views? Do you make them adaptive and following the guidelines for future expansions, or just cobble together something that works?https://pcbuilder.onl/pcpartpicker/