Before:
  runtime ale_linters/python/mypy.vim
  call ale#test#SetDirectory('/testplugin/test/command_callback')

After:
  call ale#test#RestoreDirectory()
  call ale#linter#Reset()
  let g:ale_python_mypy_executable = 'mypy'
  let g:ale_python_mypy_options = ''
  let g:ale_python_mypy_use_global = 0

Execute(The mypy callbacks should return the correct default values):
  AssertEqual
  \ 'mypy',
  \ ale_linters#python#mypy#GetExecutable(bufnr(''))
  AssertEqual
  \ 'cd ''' . g:dir . ''' && ''mypy'' --show-column-numbers  '
  \   . '--shadow-file %s %t %s',
  \ ale_linters#python#mypy#GetCommand(bufnr(''))

Execute(The mypy executable should be configurable, and escaped properly):
  let g:ale_python_mypy_executable = 'executable with spaces'

  AssertEqual
  \ 'executable with spaces',
  \ ale_linters#python#mypy#GetExecutable(bufnr(''))
  AssertEqual
  \ 'cd ''' . g:dir . ''' && ''executable with spaces'' --show-column-numbers  '
  \   . '--shadow-file %s %t %s',
  \ ale_linters#python#mypy#GetCommand(bufnr(''))

Execute(The mypy command callback should let you set options):
  let g:ale_python_mypy_options = '--some-option'

  AssertEqual
  \ 'cd ''' . g:dir . ''' && ''mypy'' --show-column-numbers --some-option '
  \   . '--shadow-file %s %t %s',
  \ ale_linters#python#mypy#GetCommand(bufnr(''))

Execute(The mypy command should switch directories to the detected project root):
  silent execute 'file ' . fnameescape(g:dir . '/python_paths/no_virtualenv/subdir/foo/bar.py')

  AssertEqual
  \ 'mypy',
  \ ale_linters#python#mypy#GetExecutable(bufnr(''))
  AssertEqual
  \ 'cd ''' . g:dir . '/python_paths/no_virtualenv/subdir'' && ''mypy'' --show-column-numbers  '
  \   . '--shadow-file %s %t %s',
  \ ale_linters#python#mypy#GetCommand(bufnr(''))

Execute(The mypy callbacks should detect virtualenv directories and switch to the project root):
  silent execute 'file ' . fnameescape(g:dir . '/python_paths/with_virtualenv/subdir/foo/bar.py')

  AssertEqual
  \ g:dir . '/python_paths/with_virtualenv/env/bin/mypy',
  \ ale_linters#python#mypy#GetExecutable(bufnr(''))
  AssertEqual
  \   'cd ''' . g:dir . '/python_paths/with_virtualenv/subdir'' && '''
  \   . g:dir . '/python_paths/with_virtualenv/env/bin/mypy'' --show-column-numbers  '
  \   . '--shadow-file %s %t %s',
  \ ale_linters#python#mypy#GetCommand(bufnr(''))

Execute(You should able able to use the global mypy instead):
  silent execute 'file ' . fnameescape(g:dir . '/python_paths/with_virtualenv/subdir/foo/bar.py')
  let g:ale_python_mypy_use_global = 1

  AssertEqual
  \ 'mypy',
  \ ale_linters#python#mypy#GetExecutable(bufnr(''))
  AssertEqual
  \ 'cd ''' . g:dir . '/python_paths/with_virtualenv/subdir'' && ''mypy'' --show-column-numbers  '
  \   . '--shadow-file %s %t %s',
  \ ale_linters#python#mypy#GetCommand(bufnr(''))