Before:
  Save g:ale_deno_executable
  runtime autoload/ale/handlers/deno.vim

After:
  unlet! b:ale_deno_executable

  call ale#linter#Reset()

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

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