Before:
  runtime autoload/ale/powershell.vim

  let g:ale_powershell_powershell_executable = 'pwsh'

After:
  if exists('g:tempname')
    call delete(g:tempname, 'rf')
  endif

  unlet! g:command
  unlet! g:tempname
  unlet! g:tempscript
  unlet! g:ale_powershell_powershell_executable

  runtime autoload/ale/util.vim

Execute(RunPowerShell should normalize mixed Windows temporary paths):
  if has('win32')
    let g:tempname = substitute(ale#util#Tempname(), '\\', '/', 'g')

    function! ale#util#Tempname() abort
      return g:tempname
    endfunction

    let g:tempscript = ale#path#GetAbsPath(g:tempname, 'script.ps1')
    let g:command = ale#powershell#RunPowerShell(
    \   bufnr(''),
    \   'powershell_powershell',
    \   ['Write-Output ''ok'''],
    \)

    AssertEqual
    \ ale#Escape('pwsh')
    \   . ' -Exe Bypass -NoProfile -File '
    \   . ale#Escape(g:tempscript)
    \   . ' %t',
    \ g:command
  endif