The user variable is shared by everyone who connects to this server.

There, the module object stored in MyDecoration by the time the initializer runs becomes an ancestor of ActionController::Base, and reloading MyDecoration is pointless, it won't affect that ancestor chain.

It is very important to understand that Ruby does not have a way to truly reload classes and modules in memory, and have that reflected everywhere they are already used. Technically, "unloading" the User class means removing the User constant via Object.send(:remove_const, "User").

rewrite all onload iframes to javascript-inserted elements

For me the diagrams make it easier to talk about what the tests do without getting bogged down by how they do it.

The element that we are going to apply the shape to with the shape-outside property to has to be floated. It also has to have a defined width and height. That's really important to know!

that can be played by up to 10 local players - turnwise.

The more important point comes from a program design perspective. Here, "programming to an interface" means focusing your design on what the code is doing, not how it does it. This is a vital distinction that pushes your design towards correctness and flexibility.