Today's topic is not only simple but quite important. While some projects have a dedicated UI developer that will make sure that templates are kept in pristine condition, there are many that don't. Instead the developers are left to create the UI and all it's niceties. As a developer I can say we generally aren't all that great at making things look pretty, but we are capable of setting up the necessities. With that said, there are some very basic things that should be kept in mind during UI development so that later on, testing is simple to create and maintain.
1. HTML tag ID's:
Ask any person who has ever created an html template, and they will tell you just how important it is to use IDs for things that appear only once. For example lets say you have a page with 2 tables, it is very important that you give each of those tables a unique id that can be used to identify them. The syntax is simple and it makes finding these elements easier when creating tests for the UI, by making the information simple to find in the DOM.
2. Don't repeat yourself(DRY)
When creating UI's it can be easy to duct tape in something simple, but it might not be the best choice. I recently had the experience of working on a project where the developers would regularly make something simple into multiple components, when one would have been cleaner and easier to test. The problem with trying to test such a system is that you are then exposed to multiple components with different ID's, names, content, etc. So when you interact with the component, you find yourself having to figure out which one is now displayed so that you can get your test to pass. Mind you that having multiple components in general is bad practice, so don't do it. Find a way to simplify your work so that you don't repeat yourself, and you'll find a project that is much easier to test and maintain.
3. Don't reinvent the wheel
If there is a simple way to do something that fits your needs, do it that way. Don't waste your time recreating it in some new way. When you are dealing with HTML for example, use a select/option like the rest of us. Whatever you do, don't go crazy and decide that you are going make drop down boxes with a series of divs. Seriously, don't recreate standard features in overly complex ways unless you are working on something so mind blowing that the standard doesn't fit your needs.
4. Use a templating framework
Whatever you do, don't use a library that is "amazing" because it offers UI development for programmers. This is just a fancy way of saying you'll do 10 times the work to get a simple template laid out than you would have if you had just used a templating framework that relies on HTML. You'll also spend 10 times more time trying to figure out how to add an ID to that one tag should you find you need to.
That's really about it. I may add to this list in the future, but these are the things where I've seen non UI developers go wrong the most. I do realize these are obviously pretty standard practice in most development and probably shouldn't need saying, but I did it anyway. Just remember, if you are a developer on a team, someone else is likely going to be testing your code. So construct your UI and code like the next person testing it is a violent psychopath that knows where you live.