new file mode 100644
--- /dev/null
+++ b/src/testdir/test_vim9_script.vim
@@ -0,0 +1,359 @@
+" Test various aspects of the Vim9 script language.
+
+" Check that "lines" inside ":def" results in an "error" message.
+func CheckDefFailure(lines, error)
+  call writefile(['def! Func()'] + a:lines + ['enddef'], 'Xdef')
+  call assert_fails('so Xdef', a:error, a:lines)
+  call delete('Xdef')
+endfunc
+
+func CheckScriptFailure(lines, error)
+  call writefile(a:lines, 'Xdef')
+  call assert_fails('so Xdef', a:error, a:lines)
+  call delete('Xdef')
+endfunc
+
+def Test_syntax()
+  let var = 234
+  let other: list<string> = ['asdf']
+enddef
+
+func Test_def_basic()
+  def SomeFunc(): string
+    return 'yes'
+  enddef
+  call assert_equal('yes', SomeFunc())
+endfunc
+
+def Test_assignment()
+  let bool1: bool = true
+  assert_equal(v:true, bool1)
+  let bool2: bool = false
+  assert_equal(v:false, bool2)
+
+  let list1: list<string> = ['sdf', 'asdf']
+  let list2: list<number> = [1, 2, 3]
+
+  " TODO: does not work yet
+  " let listS: list<string> = []
+  " let listN: list<number> = []
+
+  let dict1: dict<string> = #{key: 'value'}
+  let dict2: dict<number> = #{one: 1, two: 2}
+enddef
+
+func Test_assignment_failure()
+  call CheckDefFailure(['let var=234'], 'E1004:')
+  call CheckDefFailure(['let var =234'], 'E1004:')
+  call CheckDefFailure(['let var= 234'], 'E1004:')
+
+  call CheckDefFailure(['let true = 1'], 'E1034:')
+  call CheckDefFailure(['let false = 1'], 'E1034:')
+
+  call CheckDefFailure(['let var: list<string> = [123]'], 'expected list<string> but got list<number>')
+  call CheckDefFailure(['let var: list<number> = ["xx"]'], 'expected list<number> but got list<string>')
+
+  call CheckDefFailure(['let var: dict<string> = #{key: 123}'], 'expected dict<string> but got dict<number>')
+  call CheckDefFailure(['let var: dict<number> = #{key: "xx"}'], 'expected dict<number> but got dict<string>')
+
+  call CheckDefFailure(['let var = feedkeys("0")'], 'E1031:')
+  call CheckDefFailure(['let var: number = feedkeys("0")'], 'expected number but got void')
+endfunc
+
+func Test_const()
+  call CheckDefFailure(['const var = 234', 'var = 99'], 'E1018:')
+  call CheckDefFailure(['const one = 234', 'let one = 99'], 'E1017:')
+  call CheckDefFailure(['const two'], 'E1021:')
+endfunc
+
+def Test_block()
+  let outer = 1
+  {
+    let inner = 2
+    assert_equal(1, outer)
+    assert_equal(2, inner)
+  }
+  assert_equal(1, outer)
+enddef
+
+func Test_block_failure()
+  call CheckDefFailure(['{', 'let inner = 1', '}', 'echo inner'], 'E1001:')
+endfunc
+
+def ReturnString(): string
+  return 'string'
+enddef
+
+def ReturnNumber(): number
+  return 123
+enddef
+
+def Test_return_string()
+  assert_equal('string', ReturnString())
+  assert_equal(123, ReturnNumber())
+enddef
+
+func Increment()
+  let g:counter += 1
+endfunc
+
+def Test_call_ufunc_count()
+  g:counter = 1
+  Increment()
+  Increment()
+  Increment()
+  " works with and without :call
+  assert_equal(4, g:counter)
+  call assert_equal(4, g:counter)
+  unlet g:counter
+enddef
+
+def MyVarargs(arg: string, ...rest: list<string>): string
+  let res = arg
+  for s in rest
+    res ..= ',' .. s
+  endfor
+  return res
+enddef
+
+def Test_call_varargs()
+  assert_equal('one', MyVarargs('one'))
+  assert_equal('one,two', MyVarargs('one', 'two'))
+  assert_equal('one,two,three', MyVarargs('one', 'two', 'three'))
+enddef
+
+def Test_return_type_wrong()
+  " TODO: why is ! needed for Mac and FreeBSD?
+  CheckScriptFailure(['def! Func(): number', 'return "a"', 'enddef'], 'expected number but got string')
+  CheckScriptFailure(['def! Func(): string', 'return 1', 'enddef'], 'expected string but got number')
+  CheckScriptFailure(['def! Func(): void', 'return "a"', 'enddef'], 'expected void but got string')
+  CheckScriptFailure(['def! Func()', 'return "a"', 'enddef'], 'expected void but got string')
+enddef
+
+def Test_try_catch()
+  let l = []
+  try
+    add(l, '1')
+    throw 'wrong'
+    add(l, '2')
+  catch
+    add(l, v:exception)
+  finally
+    add(l, '3')
+  endtry
+  assert_equal(['1', 'wrong', '3'], l)
+enddef
+
+let s:export_script_lines =<< trim END
+  vim9script
+  let name: string = 'bob'
+  def Concat(arg: string): string
+    return name .. arg
+  enddef
+  let g:result = Concat('bie')
+  let g:localname = name
+
+  export const CONST = 1234
+  export let exported = 9876
+  export def Exported(): string
+    return 'Exported'
+  enddef
+END
+
+def Test_vim9script()
+  let import_script_lines =<< trim END
+    vim9script
+    import {exported, Exported} from './Xexport.vim'
+    g:imported = exported
+    g:imported_func = Exported()
+  END
+
+  writefile(import_script_lines, 'Ximport.vim')
+  writefile(s:export_script_lines, 'Xexport.vim')
+
+  source Ximport.vim
+
+  assert_equal('bobbie', g:result)
+  assert_equal('bob', g:localname)
+  assert_equal(9876, g:imported)
+  assert_equal('Exported', g:imported_func)
+  assert_false(exists('g:name'))
+
+  unlet g:result
+  unlet g:localname
+  unlet g:imported
+  unlet g:imported_func
+  delete('Ximport.vim')
+  delete('Xexport.vim')
+
+  CheckScriptFailure(['scriptversion 2', 'vim9script'], 'E1039:')
+  CheckScriptFailure(['vim9script', 'scriptversion 2'], 'E1040:')
+enddef
+
+def Test_vim9script_call()
+  let lines =<< trim END
+    vim9script
+    let var = ''
+    def MyFunc(arg: string)
+       var = arg
+    enddef
+    MyFunc('foobar')
+    assert_equal('foobar', var)
+
+    let str = 'barfoo'
+    str->MyFunc()
+    assert_equal('barfoo', var)
+
+    let g:value = 'value'
+    g:value->MyFunc()
+    assert_equal('value', var)
+
+    let listvar = []
+    def ListFunc(arg: list<number>)
+       listvar = arg
+    enddef
+    [1, 2, 3]->ListFunc()
+    assert_equal([1, 2, 3], listvar)
+
+    let dictvar = {}
+    def DictFunc(arg: dict<number>)
+       dictvar = arg
+    enddef
+    {'a': 1, 'b': 2}->DictFunc()
+    assert_equal(#{a: 1, b: 2}, dictvar)
+    #{a: 3, b: 4}->DictFunc()
+    assert_equal(#{a: 3, b: 4}, dictvar)
+  END
+  writefile(lines, 'Xcall.vim')
+  source Xcall.vim
+  delete('Xcall.vim')
+enddef
+
+def Test_vim9script_call_fail_decl()
+  let lines =<< trim END
+    vim9script
+    let var = ''
+    def MyFunc(arg: string)
+       let var = 123
+    enddef
+  END
+  writefile(lines, 'Xcall_decl.vim')
+  assert_fails('source Xcall_decl.vim', 'E1054:')
+  delete('Xcall_decl.vim')
+enddef
+
+def Test_vim9script_call_fail_const()
+  let lines =<< trim END
+    vim9script
+    const var = ''
+    def MyFunc(arg: string)
+       var = 'asdf'
+    enddef
+  END
+  writefile(lines, 'Xcall_const.vim')
+  assert_fails('source Xcall_const.vim', 'E46:')
+  delete('Xcall_const.vim')
+enddef
+
+def Test_vim9script_reload()
+  let lines =<< trim END
+    vim9script
+    const var = ''
+    let valone = 1234
+    def MyFunc(arg: string)
+       valone = 5678
+    enddef
+  END
+  let morelines =<< trim END
+    let valtwo = 222
+    export def GetValtwo(): number
+      return valtwo
+    enddef
+  END
+  writefile(lines + morelines, 'Xreload.vim')
+  source Xreload.vim
+  source Xreload.vim
+  source Xreload.vim
+
+  let testlines =<< trim END
+    vim9script
+    def TheFunc()
+      import GetValtwo from './Xreload.vim'
+      assert_equal(222, GetValtwo())
+    enddef
+    TheFunc()
+  END
+  writefile(testlines, 'Ximport.vim')
+  source Ximport.vim
+
+  " test that when not using "morelines" valtwo is still defined
+  " need to source Xreload.vim again, import doesn't reload a script
+  writefile(lines, 'Xreload.vim')
+  source Xreload.vim
+  source Ximport.vim
+
+  " cannot declare a var twice
+  lines =<< trim END
+    vim9script
+    let valone = 1234
+    let valone = 5678
+  END
+  writefile(lines, 'Xreload.vim')
+  assert_fails('source Xreload.vim', 'E1041:')
+
+  delete('Xreload.vim')
+  delete('Ximport.vim')
+enddef
+
+def Test_import_absolute()
+  let import_lines = [
+        \ 'vim9script',
+        \ 'import exported from "' .. escape(getcwd(), '\') .. '/Xexport_abs.vim"',
+        \ 'g:imported_abs = exported',
+        \ ]
+  writefile(import_lines, 'Ximport_abs.vim')
+  writefile(s:export_script_lines, 'Xexport_abs.vim')
+
+  source Ximport_abs.vim
+
+  assert_equal(9876, g:imported_abs)
+  unlet g:imported_abs
+
+  delete('Ximport_abs.vim')
+  delete('Xexport_abs.vim')
+enddef
+
+def Test_import_rtp()
+  let import_lines = [
+        \ 'vim9script',
+        \ 'import exported from "Xexport_rtp.vim"',
+        \ 'g:imported_rtp = exported',
+        \ ]
+  writefile(import_lines, 'Ximport_rtp.vim')
+  mkdir('import')
+  writefile(s:export_script_lines, 'import/Xexport_rtp.vim')
+
+  let save_rtp = &rtp
+  &rtp = getcwd()
+  source Ximport_rtp.vim
+  &rtp = save_rtp
+
+  assert_equal(9876, g:imported_rtp)
+  unlet g:imported_rtp
+
+  delete('Ximport_rtp.vim')
+  delete('import/Xexport_rtp.vim')
+  delete('import', 'd')
+enddef
+
+def Test_fixed_size_list()
+  " will be allocated as one piece of memory, check that changes work
+  let l = [1, 2, 3, 4]
+  l->remove(0)
+  l->add(5)
+  l->insert(99, 1)
+  call assert_equal([2, 99, 3, 4, 5], l)
+enddef
+
+
+" vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker