When you publish a website or a web application to the public, users expect it to work. Links are supposed to take their places, and buttons are supposed to do things. They may not have the technical knowhow to look in good their browser console or observe network traffic. They may even have good reason to disable JavaScript on their browser.

The truth is, sometimes websites don't work because of hardware, software, or user error, but at other times the cause comes from the developer's buggy code. Maybe the code was pieced together from a cut-and-paste collage of code samples and stack overflow answers. Then the developer rushes to test the application once or twice, using the same workflow they use every time they write a component.

Maybe, though, something changed outside of the developer's control. Maybe a feature attribute that once held numeric values now contains strings. Maybe the API was updated and there was a fundamental change in the application. Maybe a REST...