Imagine, if you will, a typical navigation menu on a typical website, with submenus when we hover over a link. We might at first try to build it as a single isolated component. If we use a pattern library, this is easy to do. But how we choose to structure our component within the pattern library has a big impact on how easy it will be to test and update it.
This state of affairs doesn't seem ideal. What happens if we break down our components into their smallest constituent parts? If we structure them all with modularity in mind? If we set up our component preview files to account for missing resources? Our components will gain a super power: Ultra Testability!
We build from the smallest units up. We can now check each part with its own inherent states in isolation. We can immediately see where regressions, combinatory errors, or edge cases crop up. We make no assumptions about where these units fit within the larger structure. As a result, we can use these smaller pieces elsewhere without modification. Once we've created all the parts, assembling the whole is as simple as putting them together. Then we need test only the states of the larger assembly. The result is robust, flexible, and easy to change. Congratulations, you have created a Super Component!
I've found it useful to create content generators for creating specific text when you want it, or random text if not. You can set ranges of likely text or item lengths to keep things reasonable. The node library faker.js is helpful for this.