Emacs dividing window with docked tests on the correct one

Question

I am looking for a way to do the following in emacs: every time I open a test file (ending with Test, Spec, etc.), I would like it to open in the right pane, the rest of the files should be displayed in the left pane. It would be even better if I opened the source file, and if there is a file with the same name, but with the completion of * Spec / * Test, it should open automatically. I'm sure it can be done in emacs, but how?