test: move oldtests to test directory (#22536)

The new oldtest directory is in test/old/testdir. The reason for this is
that many tests have hardcoded the parent directory name to be
'testdir'.

test/old/testdir/test_compiler.vim

@@ -0,0 +1,78 @@
+" Test the :compiler command
+
+source check.vim
+source shared.vim
+
+func Test_compiler()
+  CheckExecutable perl
+  CheckFeature quickfix
+
+  " $LANG changes the output of Perl.
+  if $LANG != ''
+    unlet $LANG
+  endif
+
+  " %:S does not work properly with 'shellslash' set
+  let save_shellslash = &shellslash
+  set noshellslash
+
+  e Xfoo.pl
+  compiler perl
+  call assert_equal('perl', b:current_compiler)
+  call assert_fails('let g:current_compiler', 'E121:')
+
+  let verbose_efm = execute('verbose set efm')
+  call assert_match('Last set from .*[/\\]compiler[/\\]perl.vim ', verbose_efm)
+
+  call setline(1, ['#!/usr/bin/perl -w', 'use strict;', 'my $foo=1'])
+  w!
+  call feedkeys(":make\<CR>\<CR>", 'tx')
+  call assert_fails('clist', 'E42:')
+
+  call setline(1, ['#!/usr/bin/perl -w', 'use strict;', '$foo=1'])
+  w!
+  call feedkeys(":make\<CR>\<CR>", 'tx')
+  let a=execute('clist')
+  call assert_match('\n \d\+ Xfoo.pl:3: Global symbol "$foo" '
+  \ .               'requires explicit package name', a)
+
+
+  let &shellslash = save_shellslash
+  call delete('Xfoo.pl')
+  bw!
+endfunc
+
+func GetCompilerNames()
+  return glob('$VIMRUNTIME/compiler/*.vim', 0, 1)
+       \ ->map({i, v -> substitute(v, '.*[\\/]\([a-zA-Z0-9_\-]*\).vim', '\1', '')})
+       \ ->sort()
+endfunc
+
+func Test_compiler_without_arg()
+  let runtime = substitute($VIMRUNTIME, '\\', '/', 'g')
+  let a = split(execute('compiler'))
+  let exp = GetCompilerNames()
+  call assert_match(runtime .. '/compiler/' .. exp[0] .. '.vim$',  a[0])
+  call assert_match(runtime .. '/compiler/' .. exp[1] .. '.vim$',  a[1])
+  call assert_match(runtime .. '/compiler/' .. exp[-1] .. '.vim$', a[-1])
+endfunc
+
+func Test_compiler_completion()
+  let clist = GetCompilerNames()->join(' ')
+  call feedkeys(":compiler \<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_match('^"compiler ' .. clist .. '$', @:)
+
+  call feedkeys(":compiler p\<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_match('"compiler pbx perl\( p[a-z]\+\)\+ pylint pyunit', @:)
+
+  call feedkeys(":compiler! p\<C-A>\<C-B>\"\<CR>", 'tx')
+  call assert_match('"compiler! pbx perl\( p[a-z]\+\)\+ pylint pyunit', @:)
+endfunc
+
+func Test_compiler_error()
+  let g:current_compiler = 'abc'
+  call assert_fails('compiler doesnotexist', 'E666:')
+  call assert_equal('abc', g:current_compiler)
+  call assert_fails('compiler! doesnotexist', 'E666:')
+  unlet! g:current_compiler
+endfunc