Before:
  Save g:ale_python_isort_executable

  " Use an invalid global executable, so we don't match it.
  let g:ale_python_isort_executable = 'xxxinvalid'

  call ale#test#SetDirectory('/testplugin/test/fixers')
  silent cd ..
  silent cd command_callback
  let g:dir = getcwd()

After:
  Restore

  call ale#test#RestoreDirectory()

Execute(The isort callback should return the correct default values):
  AssertEqual
  \ 0,
  \ ale#fixers#isort#Fix(bufnr(''))

  silent execute 'file ' . fnameescape(g:dir . '/python_paths/with_virtualenv/subdir/foo/bar.py')
  AssertEqual
  \ {'command': "'" . g:dir . "/python_paths/with_virtualenv/env/bin/isort' -" },
  \ ale#fixers#isort#Fix(bufnr(''))