while the implementation is not tied to screen chars, it is a reasonable
expectation to support the same size. If nvim is able to display a
multibyte character, it will accept the same character as input,
including in normal mode commands like r{char}
Specifically, functions that are run in the context of the test runner
are put in module `test/testutil.lua` while the functions that are run
in the context of the test session are put in
`test/functional/testnvim.lua`.
Closes https://github.com/neovim/neovim/issues/27004.
