Before:
  Save g:ale_proselint_executable
  runtime autoload/ale/proselint.vim

After:
  Restore

Execute(Default executable should be detected correctly):
  AssertEqual
  \ 'proselint',
  \ ale#proselint#GetExecutable(bufnr(''))

Execute(User specified executable should override default):
  let g:ale_proselint_executable = '/path/to/proselint-bin'
  AssertEqual
  \ '/path/to/proselint-bin',
  \ ale#proselint#GetExecutable(bufnr(''))