new file mode 100644
--- /dev/null
+++ b/src/testdir/test_vim9_builtin.vim
@@ -0,0 +1,554 @@
+" Test using builtin functions in the Vim9 script language.
+
+source check.vim
+source vim9.vim
+
+" Test for passing too many or too few arguments to builtin functions
+func Test_internalfunc_arg_error()
+  let l =<< trim END
+    def! FArgErr(): float
+      return ceil(1.1, 2)
+    enddef
+    defcompile
+  END
+  call writefile(l, 'Xinvalidarg')
+  call assert_fails('so Xinvalidarg', 'E118:', '', 1, 'FArgErr')
+  let l =<< trim END
+    def! FArgErr(): float
+      return ceil()
+    enddef
+    defcompile
+  END
+  call writefile(l, 'Xinvalidarg')
+  call assert_fails('so Xinvalidarg', 'E119:', '', 1, 'FArgErr')
+  call delete('Xinvalidarg')
+endfunc
+
+" Test for builtin functions returning different types
+func Test_InternalFuncRetType()
+  let lines =<< trim END
+    def RetFloat(): float
+      return ceil(1.456)
+    enddef
+
+    def RetListAny(): list<any>
+      return items({'k': 'v'})
+    enddef
+
+    def RetListString(): list<string>
+      return split('a:b:c', ':')
+    enddef
+
+    def RetListDictAny(): list<dict<any>>
+      return getbufinfo()
+    enddef
+
+    def RetDictNumber(): dict<number>
+      return wordcount()
+    enddef
+
+    def RetDictString(): dict<string>
+      return environ()
+    enddef
+  END
+  call writefile(lines, 'Xscript')
+  source Xscript
+
+  call RetFloat()->assert_equal(2.0)
+  call RetListAny()->assert_equal([['k', 'v']])
+  call RetListString()->assert_equal(['a', 'b', 'c'])
+  call RetListDictAny()->assert_notequal([])
+  call RetDictNumber()->assert_notequal({})
+  call RetDictString()->assert_notequal({})
+  call delete('Xscript')
+endfunc
+
+def Test_abs()
+  assert_equal(0, abs(0))
+  assert_equal(2, abs(-2))
+  assert_equal(3, abs(3))
+  CheckDefFailure(['abs("text")'], 'E1013: Argument 1: type mismatch, expected number but got string', 1)
+  if has('float')
+    assert_equal(0, abs(0))
+    assert_equal(2.0, abs(-2.0))
+    assert_equal(3.0, abs(3.0))
+  endif
+enddef
+
+def Test_add_list()
+  var l: list<number>  # defaults to empty list
+  add(l, 9)
+  assert_equal([9], l)
+
+  var lines =<< trim END
+      var l: list<number>
+      add(l, "x")
+  END
+  CheckDefFailure(lines, 'E1012:', 2)
+
+  lines =<< trim END
+      var l: list<number> = test_null_list()
+      add(l, 123)
+  END
+  CheckDefExecFailure(lines, 'E1130:', 2)
+enddef
+
+def Test_add_blob()
+  var b1: blob = 0z12
+  add(b1, 0x34)
+  assert_equal(0z1234, b1)
+
+  var b2: blob # defaults to empty blob
+  add(b2, 0x67)
+  assert_equal(0z67, b2)
+
+  var lines =<< trim END
+      var b: blob
+      add(b, "x")
+  END
+  CheckDefFailure(lines, 'E1012:', 2)
+
+  lines =<< trim END
+      var b: blob = test_null_blob()
+      add(b, 123)
+  END
+  CheckDefExecFailure(lines, 'E1131:', 2)
+enddef
+
+def Test_bufname()
+  split SomeFile
+  bufname('%')->assert_equal('SomeFile')
+  edit OtherFile
+  bufname('#')->assert_equal('SomeFile')
+  close
+enddef
+
+def Test_bufnr()
+  var buf = bufnr()
+  bufnr('%')->assert_equal(buf)
+
+  buf = bufnr('Xdummy', true)
+  buf->assert_notequal(-1)
+  exe 'bwipe! ' .. buf
+enddef
+
+def Test_bufwinid()
+  var origwin = win_getid()
+  below split SomeFile
+  var SomeFileID = win_getid()
+  below split OtherFile
+  below split SomeFile
+  bufwinid('SomeFile')->assert_equal(SomeFileID)
+
+  win_gotoid(origwin)
+  only
+  bwipe SomeFile
+  bwipe OtherFile
+enddef
+
+def Test_call_call()
+  var l = [3, 2, 1]
+  call('reverse', [l])
+  l->assert_equal([1, 2, 3])
+enddef
+
+def Test_char2nr()
+  char2nr('あ', true)->assert_equal(12354)
+enddef
+
+def Test_col()
+  new
+  setline(1, 'asdf')
+  col([1, '$'])->assert_equal(5)
+enddef
+
+def Test_copy_return_type()
+  var l = copy([1, 2, 3])
+  var res = 0
+  for n in l
+    res += n
+  endfor
+  res->assert_equal(6)
+
+  var dl = deepcopy([1, 2, 3])
+  res = 0
+  for n in dl
+    res += n
+  endfor
+  res->assert_equal(6)
+
+  dl = deepcopy([1, 2, 3], true)
+enddef
+
+def Test_count()
+  count('ABC ABC ABC', 'b', true)->assert_equal(3)
+  count('ABC ABC ABC', 'b', false)->assert_equal(0)
+enddef
+
+def Test_expand()
+  split SomeFile
+  expand('%', true, true)->assert_equal(['SomeFile'])
+  close
+enddef
+
+def Test_extend_return_type()
+  var l = extend([1, 2], [3])
+  var res = 0
+  for n in l
+    res += n
+  endfor
+  res->assert_equal(6)
+enddef
+
+
+def Wrong_dict_key_type(items: list<number>): list<number>
+  return filter(items, {_, val -> get({val: 1}, 'x')})
+enddef
+
+def Test_filter_wrong_dict_key_type()
+  assert_fails('Wrong_dict_key_type([1, 2, 3])', 'E1012:')
+enddef
+
+def Test_filter_return_type()
+  var l = filter([1, 2, 3], {-> 1})
+  var res = 0
+  for n in l
+    res += n
+  endfor
+  res->assert_equal(6)
+enddef
+
+
+def Test_garbagecollect()
+  garbagecollect(true)
+enddef
+
+def Test_getbufinfo()
+  var bufinfo = getbufinfo(bufnr())
+  getbufinfo('%')->assert_equal(bufinfo)
+
+  edit Xtestfile1
+  hide edit Xtestfile2
+  hide enew
+  getbufinfo(#{bufloaded: true, buflisted: true, bufmodified: false})
+      ->len()->assert_equal(3)
+  bwipe Xtestfile1 Xtestfile2
+enddef
+
+def Test_getbufline()
+  e SomeFile
+  var buf = bufnr()
+  e #
+  var lines = ['aaa', 'bbb', 'ccc']
+  setbufline(buf, 1, lines)
+  getbufline('#', 1, '$')->assert_equal(lines)
+
+  bwipe!
+enddef
+
+def Test_getchangelist()
+  new
+  setline(1, 'some text')
+  var changelist = bufnr()->getchangelist()
+  getchangelist('%')->assert_equal(changelist)
+  bwipe!
+enddef
+
+def Test_getchar()
+  while getchar(0)
+  endwhile
+  getchar(true)->assert_equal(0)
+enddef
+
+def Test_getcompletion()
+  set wildignore=*.vim,*~
+  var l = getcompletion('run', 'file', true)
+  l->assert_equal([])
+  set wildignore&
+enddef
+
+def Test_getloclist_return_type()
+  var l = getloclist(1)
+  l->assert_equal([])
+
+  var d = getloclist(1, #{items: 0})
+  d->assert_equal(#{items: []})
+enddef
+
+def Test_getqflist_return_type()
+  var l = getqflist()
+  l->assert_equal([])
+
+  var d = getqflist(#{items: 0})
+  d->assert_equal(#{items: []})
+enddef
+
+def Test_getreg()
+  var lines = ['aaa', 'bbb', 'ccc']
+  setreg('a', lines)
+  getreg('a', true, true)->assert_equal(lines)
+enddef
+
+def Test_getreg_return_type()
+  var s1: string = getreg('"')
+  var s2: string = getreg('"', 1)
+  var s3: list<string> = getreg('"', 1, 1)
+enddef
+
+def Test_glob()
+  glob('runtest.vim', true, true, true)->assert_equal(['runtest.vim'])
+enddef
+
+def Test_globpath()
+  globpath('.', 'runtest.vim', true, true, true)->assert_equal(['./runtest.vim'])
+enddef
+
+def Test_has()
+  has('eval', true)->assert_equal(1)
+enddef
+
+def Test_hasmapto()
+  hasmapto('foobar', 'i', true)->assert_equal(0)
+  iabbrev foo foobar
+  hasmapto('foobar', 'i', true)->assert_equal(1)
+  iunabbrev foo
+enddef
+
+def Test_index()
+  index(['a', 'b', 'a', 'B'], 'b', 2, true)->assert_equal(3)
+enddef
+
+def Test_insert_return_type()
+  var l = insert([2, 1], 3)
+  var res = 0
+  for n in l
+    res += n
+  endfor
+  res->assert_equal(6)
+enddef
+
+def Test_keys_return_type()
+  const var: list<string> = #{a: 1, b: 2}->keys()
+  var->assert_equal(['a', 'b'])
+enddef
+
+def Test_list2str_str2list_utf8()
+  var s = "\u3042\u3044"
+  var l = [0x3042, 0x3044]
+  str2list(s, true)->assert_equal(l)
+  list2str(l, true)->assert_equal(s)
+enddef
+
+def SID(): number
+  return expand('<SID>')
+          ->matchstr('<SNR>\zs\d\+\ze_$')
+          ->str2nr()
+enddef
+
+def Test_maparg()
+  var lnum = str2nr(expand('<sflnum>'))
+  map foo bar
+  maparg('foo', '', false, true)->assert_equal(#{
+        lnum: lnum + 1,
+        script: 0,
+        mode: ' ',
+        silent: 0,
+        noremap: 0,
+        lhs: 'foo',
+        lhsraw: 'foo',
+        nowait: 0,
+        expr: 0,
+        sid: SID(),
+        rhs: 'bar',
+        buffer: 0})
+  unmap foo
+enddef
+
+def Test_mapcheck()
+  iabbrev foo foobar
+  mapcheck('foo', 'i', true)->assert_equal('foobar')
+  iunabbrev foo
+enddef
+
+def Test_maparg_mapset()
+  nnoremap <F3> :echo "hit F3"<CR>
+  var mapsave = maparg('<F3>', 'n', false, true)
+  mapset('n', false, mapsave)
+
+  nunmap <F3>
+enddef
+
+def Test_nr2char()
+  nr2char(97, true)->assert_equal('a')
+enddef
+
+def Test_readdir()
+   eval expand('sautest')->readdir({e -> e[0] !=# '.'})
+   eval expand('sautest')->readdirex({e -> e.name[0] !=# '.'})
+enddef
+
+def Test_remove_return_type()
+  var l = remove(#{one: [1, 2], two: [3, 4]}, 'one')
+  var res = 0
+  for n in l
+    res += n
+  endfor
+  res->assert_equal(3)
+enddef
+
+def Test_reverse_return_type()
+  var l = reverse([1, 2, 3])
+  var res = 0
+  for n in l
+    res += n
+  endfor
+  res->assert_equal(6)
+enddef
+
+def Test_search()
+  new
+  setline(1, ['foo', 'bar'])
+  var val = 0
+  # skip expr returns boolean
+  search('bar', 'W', 0, 0, {-> val == 1})->assert_equal(2)
+  :1
+  search('bar', 'W', 0, 0, {-> val == 0})->assert_equal(0)
+  # skip expr returns number, only 0 and 1 are accepted
+  :1
+  search('bar', 'W', 0, 0, {-> 0})->assert_equal(2)
+  :1
+  search('bar', 'W', 0, 0, {-> 1})->assert_equal(0)
+  assert_fails("search('bar', '', 0, 0, {-> -1})", 'E1023:')
+  assert_fails("search('bar', '', 0, 0, {-> -1})", 'E1023:')
+enddef
+
+def Test_searchcount()
+  new
+  setline(1, "foo bar")
+  :/foo
+  searchcount(#{recompute: true})
+      ->assert_equal(#{
+          exact_match: 1,
+          current: 1,
+          total: 1,
+          maxcount: 99,
+          incomplete: 0})
+  bwipe!
+enddef
+
+def Test_searchdecl()
+  searchdecl('blah', true, true)->assert_equal(1)
+enddef
+
+def Test_setbufvar()
+  setbufvar(bufnr('%'), '&syntax', 'vim')
+  &syntax->assert_equal('vim')
+  setbufvar(bufnr('%'), '&ts', 16)
+  &ts->assert_equal(16)
+  settabwinvar(1, 1, '&syntax', 'vam')
+  &syntax->assert_equal('vam')
+  settabwinvar(1, 1, '&ts', 15)
+  &ts->assert_equal(15)
+  setlocal ts=8
+
+  setbufvar('%', 'myvar', 123)
+  getbufvar('%', 'myvar')->assert_equal(123)
+enddef
+
+def Test_setloclist()
+  var items = [#{filename: '/tmp/file', lnum: 1, valid: true}]
+  var what = #{items: items}
+  setqflist([], ' ', what)
+  setloclist(0, [], ' ', what)
+enddef
+
+def Test_setreg()
+  setreg('a', ['aaa', 'bbb', 'ccc'])
+  var reginfo = getreginfo('a')
+  setreg('a', reginfo)
+  getreginfo('a')->assert_equal(reginfo)
+enddef 
+
+def Test_spellsuggest()
+  if !has('spell')
+    MissingFeature 'spell'
+  else
+    spellsuggest('marrch', 1, true)->assert_equal(['March'])
+  endif
+enddef
+
+def Test_sort_return_type()
+  var res: list<number>
+  res = [1, 2, 3]->sort()
+enddef
+
+def Test_sort_argument()
+  var res = ['b', 'a', 'c']->sort('i')
+  res->assert_equal(['a', 'b', 'c'])
+enddef
+
+def Test_split()
+  split('  aa  bb  ', '\W\+', true)->assert_equal(['', 'aa', 'bb', ''])
+enddef
+
+def Test_str2nr()
+  str2nr("1'000'000", 10, true)->assert_equal(1000000)
+enddef
+
+def Test_strchars()
+  strchars("A\u20dd", true)->assert_equal(1)
+enddef
+
+def Test_submatch()
+  var pat = 'A\(.\)\(.\)\(.\)\(.\)\(.\)\(.\)\(.\)\(.\)\(.\)'
+  var Rep = {-> range(10)->map({_, v -> submatch(v, true)})->string()}
+  var actual = substitute('A123456789', pat, Rep, '')
+  var expected = "[['A123456789'], ['1'], ['2'], ['3'], ['4'], ['5'], ['6'], ['7'], ['8'], ['9']]"
+  actual->assert_equal(expected)
+enddef
+
+def Test_synID()
+  new
+  setline(1, "text")
+  synID(1, 1, true)->assert_equal(0)
+  bwipe!
+enddef
+
+def Test_term_gettty()
+  if !has('terminal')
+    MissingFeature 'terminal'
+  else
+    var buf = Run_shell_in_terminal({})
+    term_gettty(buf, true)->assert_notequal('')
+    StopShellInTerminal(buf)
+  endif
+enddef
+
+def Test_term_start()
+  if !has('terminal')
+    MissingFeature 'terminal'
+  else
+    botright new
+    var winnr = winnr()
+    term_start(&shell, #{curwin: true})
+    winnr()->assert_equal(winnr)
+    bwipe!
+  endif
+enddef
+
+def Test_timer_paused()
+  var id = timer_start(50, {-> 0})
+  timer_pause(id, true)
+  var info = timer_info(id)
+  info[0]['paused']->assert_equal(1)
+  timer_stop(id)
+enddef
+
+def Test_win_splitmove()
+  split
+  win_splitmove(1, 2, #{vertical: true, rightbelow: true})
+  close
+enddef
+
+
+" vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker