Hey guys! This is my wrapping PR for component unit testing as I promised before.

I fixed all items you had problems with (as mentioned in #517):

1. CustomError, ServerError, InternalError were requiring children even though you had a check children || "alt text" in there which didn't make sense and test exposed that (also fixed the issue)
2. You almost don't use alt property on images, most of my tests exposed that but I decided to not change it for now, if you want me to I am happy to open separate prs to fix that!
3. Most of your html input/labels dont have htmlFor and id for input/label pair, I can also open additional prs to fix that to enhance the repo

I also added final tests to all components to make sure they are functioning correctly and moving forward if there will be any changes you will be able to catch any issues in advance!