diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index ad2dc2b..f798916 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -2483,4 +2483,28 @@
   delfunc ReadFileCmd
 endfunc
 
+" Test for passing invalid arguments to autocmd
+func Test_autocmd_invalid_args()
+  " Additional character after * for event
+  call assert_fails('autocmd *a Xfile set ff=unix', 'E215:')
+  augroup Test
+  augroup END
+  " Invalid autocmd event
+  call assert_fails('autocmd Bufabc Xfile set ft=vim', 'E216:')
+  " Invalid autocmd event in a autocmd group
+  call assert_fails('autocmd Test Bufabc Xfile set ft=vim', 'E216:')
+  augroup! Test
+  " Execute all autocmds
+  call assert_fails('doautocmd * BufEnter', 'E217:')
+  call assert_fails('augroup! x1a2b3', 'E367:')
+  call assert_fails('autocmd BufNew <buffer=999> pwd', 'E680:')
+endfunc
+
+" Test for deep nesting of autocmds
+func Test_autocmd_deep_nesting()
+  autocmd BufEnter Xfile doautocmd BufEnter Xfile
+  call assert_fails('doautocmd BufEnter Xfile', 'E218:')
+  autocmd! BufEnter Xfile
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/testdir/test_clientserver.vim b/src/testdir/test_clientserver.vim
index 8a333aa..7936227 100644
--- a/src/testdir/test_clientserver.vim
+++ b/src/testdir/test_clientserver.vim
@@ -2,6 +2,11 @@
 
 source check.vim
 CheckFeature job
+
+if !has('clientserver')
+  call assert_fails('call remote_startserver("local")', 'E942:')
+endif
+
 CheckFeature clientserver
 
 source shared.vim
@@ -161,6 +166,7 @@
 
   call assert_fails("let x = remote_peek([])", 'E730:')
   call assert_fails("let x = remote_read('vim10')", 'E277:')
+  call assert_fails("call server2client('abc', 'xyz')", 'E258:')
 endfunc
 
 " Uncomment this line to get a debugging log
diff --git a/src/testdir/test_digraph.vim b/src/testdir/test_digraph.vim
index 1feeef2..3e3dfa8 100644
--- a/src/testdir/test_digraph.vim
+++ b/src/testdir/test_digraph.vim
@@ -210,6 +210,8 @@
   call Put_Dig("00")
   call Put_Dig("el")
   call assert_equal(['␀', 'ü', '∞', 'l'], getline(line('.')-3,line('.')))
+  call assert_fails('exe "digraph a\<Esc> 100"', 'E104:')
+  call assert_fails('exe "digraph \<Esc>a 100"', 'E104:')
   bw!
 endfunc
 
@@ -475,4 +477,15 @@
   bwipe!
 endfunc
 
+" Test for error in a keymap file
+func Test_loadkeymap_error()
+  if !has('keymap')
+    return
+  endif
+  call assert_fails('loadkeymap', 'E105:')
+  call writefile(['loadkeymap', 'a'], 'Xkeymap')
+  call assert_fails('source Xkeymap', 'E791:')
+  call delete('Xkeymap')
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/testdir/test_expand.vim b/src/testdir/test_expand.vim
index 383921b..8606223 100644
--- a/src/testdir/test_expand.vim
+++ b/src/testdir/test_expand.vim
@@ -131,6 +131,7 @@
   call assert_equal(4, winnr('$'))
   call assert_equal('foo!', bufname(winbufnr(1)))
   call assert_equal('foo', bufname(winbufnr(2)))
+  call assert_fails('e %:s/.*//', 'E500:')
   %bwipe!
 endfunc
 
diff --git a/src/testdir/test_expr.vim b/src/testdir/test_expr.vim
index 13180e6..116f713 100644
--- a/src/testdir/test_expr.vim
+++ b/src/testdir/test_expr.vim
@@ -502,6 +502,7 @@
   call assert_fails('echo funcref("{")', 'E475:')
   let OneByRef = funcref("One", repeat(["foo"], 20))
   call assert_fails('let OneByRef = funcref("One", repeat(["foo"], 21))', 'E118:')
+  call assert_fails('echo function("min") =~ function("min")', 'E694:')
 endfunc
 
 func Test_setmatches()
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 653654f..427e404 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -1966,6 +1966,7 @@
   execute "normal! a\<C-r>=[complete(col('.'), range(10)), ''][1]\<CR>"
   " complete_info()
   execute "normal! a\<C-r>=[complete(col('.'), range(10)), ''][1]\<CR>\<C-r>=[complete_info(range(5)), ''][1]\<CR>"
+  call assert_fails('call complete(1, ["a"])', 'E785:')
 
   " copy()
   call assert_equal([1, 2, 3], copy(range(1, 3)))
diff --git a/src/testdir/test_gui.vim b/src/testdir/test_gui.vim
index 54ba588..af4ce24 100644
--- a/src/testdir/test_gui.vim
+++ b/src/testdir/test_gui.vim
@@ -388,6 +388,11 @@
     call assert_equal('Monospace 10', getfontname())
   endif
 
+  if has('win32')
+    " Invalid font names are accepted in GTK GUI
+    call assert_fails('set guifont=xa1bc23d7f', 'E596:')
+  endif
+
   if has('xfontset')
     let &guifontset = guifontset_saved
   endif
@@ -402,6 +407,8 @@
   CheckFeature xfontset
   let skipped = ''
 
+  call assert_fails('set guifontset=*', 'E597:')
+
   let ctype_saved = v:ctype
 
   " First, since XCreateFontSet(3) is very sensitive to locale, fonts must
@@ -468,6 +475,7 @@
 endfunc
 
 func Test_set_guifontwide()
+  call assert_fails('set guifontwide=*', 'E533:')
   let skipped = ''
 
   if !g:x11_based_gui
@@ -785,6 +793,7 @@
   " It's enough to check the current value since setting 'term' to anything
   " other than builtin_gui makes no sense at all.
   call assert_equal('builtin_gui', &term)
+  call assert_fails('set term=xterm', 'E530:')
 endfunc
 
 func Test_windowid_variable()
diff --git a/src/testdir/test_highlight.vim b/src/testdir/test_highlight.vim
index ac6a101..dfc9e24 100644
--- a/src/testdir/test_highlight.vim
+++ b/src/testdir/test_highlight.vim
@@ -689,10 +689,28 @@
 endfunc
 
 " Do this test last, sometimes restoring the columns doesn't work
-function Test_z_no_space_before_xxx()
+func Test_z_no_space_before_xxx()
   let l:org_columns = &columns
   set columns=17
   let l:hi_StatusLineTermNC = join(split(execute('hi StatusLineTermNC')))
   call assert_match('StatusLineTermNC xxx', l:hi_StatusLineTermNC)
   let &columns = l:org_columns
-endfunction
+endfunc
+
+" Test for :highlight command errors
+func Test_highlight_cmd_errors()
+  if has('gui_running')
+    " This test doesn't fail in the MS-Windows console version.
+    call assert_fails('hi Xcomment ctermfg=fg', 'E419:')
+    call assert_fails('hi Xcomment ctermfg=bg', 'E420:')
+  endif
+
+  " Try using a very long terminal code. Define a dummy terminal code for this
+  " test.
+  let &t_fo = "\<Esc>1;"
+  let c = repeat("t_fo,", 100) . "t_fo"
+  call assert_fails('exe "hi Xgroup1 start=" . c', 'E422:')
+  let &t_fo = ""
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/testdir/test_ins_complete.vim b/src/testdir/test_ins_complete.vim
index 3a83577..b7893ff 100644
--- a/src/testdir/test_ins_complete.vim
+++ b/src/testdir/test_ins_complete.vim
@@ -465,3 +465,23 @@
   set tags&
   %bwipe!
 endfunc
+
+" Test for 'completefunc' deleting text
+func Test_completefunc_error()
+  new
+  func CompleteFunc(findstart, base)
+    if a:findstart == 1
+      normal dd
+      return col('.') - 1
+    endif
+    return ['a', 'b']
+  endfunc
+  set completefunc=CompleteFunc
+  call setline(1, ['', 'abcd', ''])
+  call assert_fails('exe "normal 2G$a\<C-X>\<C-U>"', 'E840:')
+  set completefunc&
+  delfunc CompleteFunc
+  close!
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/testdir/test_lambda.vim b/src/testdir/test_lambda.vim
index bc3d5ac..44ca911 100644
--- a/src/testdir/test_lambda.vim
+++ b/src/testdir/test_lambda.vim
@@ -311,4 +311,20 @@
   call assert_fails('ec{@{->{d->()()', 'E15')
 endfunc
 
+func Test_closure_error()
+  let l =<< trim END
+    func F1() closure
+      return 1
+    endfunc
+  END
+  call writefile(l, 'Xscript')
+  let caught_932 = 0
+  try
+    source Xscript
+  catch /E932:/
+    let caught_932 = 1
+  endtry
+  call assert_equal(1, caught_932)
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/testdir/test_listdict.vim b/src/testdir/test_listdict.vim
index 045dbb0..9db1035 100644
--- a/src/testdir/test_listdict.vim
+++ b/src/testdir/test_listdict.vim
@@ -633,6 +633,7 @@
   endif
 
   call assert_fails('call reverse("")', 'E899:')
+  call assert_fails('call uniq([1, 2], {x, y -> []})', 'E882:')
 endfunc
 
 " splitting a string to a List using split()
diff --git a/src/testdir/test_normal.vim b/src/testdir/test_normal.vim
index 83a95f9..d8afeea 100644
--- a/src/testdir/test_normal.vim
+++ b/src/testdir/test_normal.vim
@@ -364,6 +364,7 @@
   " clean up
   unmap <buffer> ,,
   set opfunc=
+  call assert_fails('normal Vg@', 'E774:')
   bw!
   unlet! g:opt
 endfunc
diff --git a/src/testdir/test_options.vim b/src/testdir/test_options.vim
index f111894..ef3ae1a 100644
--- a/src/testdir/test_options.vim
+++ b/src/testdir/test_options.vim
@@ -195,6 +195,7 @@
   new
   call feedkeys("i\<C-N>\<Esc>", 'xt')
   bwipe!
+  call assert_fails('set complete=ix', 'E535:')
   set complete&
 endfun
 
@@ -381,6 +382,10 @@
 
   set ttytype&
   call assert_equal(&ttytype, &term)
+
+  if has('gui') && !has('gui_running')
+    call assert_fails('set term=gui', 'E531:')
+  endif
 endfunc
 
 func Test_set_all()
diff --git a/src/testdir/test_preview.vim b/src/testdir/test_preview.vim
index a85798b..628ad2b 100644
--- a/src/testdir/test_preview.vim
+++ b/src/testdir/test_preview.vim
@@ -13,3 +13,50 @@
   call assert_equal(wincount, winnr('$'))
   bwipe
 endfunc
+
+func Test_window_preview()
+  CheckFeature quickfix
+
+  " Open a preview window
+  pedit Xa
+  call assert_equal(2, winnr('$'))
+  call assert_equal(0, &previewwindow)
+
+  " Go to the preview window
+  wincmd P
+  call assert_equal(1, &previewwindow)
+
+  " Close preview window
+  wincmd z
+  call assert_equal(1, winnr('$'))
+  call assert_equal(0, &previewwindow)
+
+  call assert_fails('wincmd P', 'E441:')
+endfunc
+
+func Test_window_preview_from_help()
+  CheckFeature quickfix
+
+  filetype on
+  call writefile(['/* some C code */'], 'Xpreview.c')
+  help
+  pedit Xpreview.c
+  wincmd P
+  call assert_equal(1, &previewwindow)
+  call assert_equal('c', &filetype)
+  wincmd z
+
+  filetype off
+  close
+  call delete('Xpreview.c')
+endfunc
+
+func Test_multiple_preview_windows()
+  new
+  set previewwindow
+  new
+  call assert_fails('set previewwindow', 'E590:')
+  %bw!
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/testdir/test_user_func.vim b/src/testdir/test_user_func.vim
index 433a65b..c8f8d07 100644
--- a/src/testdir/test_user_func.vim
+++ b/src/testdir/test_user_func.vim
@@ -169,3 +169,10 @@
 func Test_failed_call_in_try()
   try | call UnknownFunc() | catch | endtry
 endfunc
+
+" Test for listing user-defined functions
+func Test_function_list()
+  call assert_fails("function Xabc", 'E123:')
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 74653b1..5554b2d 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -168,10 +168,12 @@
 
   CheckScriptFailure(['def Func(): list', 'return []', 'enddef'], 'E1008:')
   CheckScriptFailure(['def Func(): dict', 'return {}', 'enddef'], 'E1008:')
+  CheckScriptFailure(['def Func()', 'return 1'], 'E1057:')
 enddef
 
 def Test_arg_type_wrong()
   CheckScriptFailure(['def Func3(items: list)', 'echo "a"', 'enddef'], 'E1008: Missing <type>')
+  CheckScriptFailure(['def Func4(...)', 'echo "a"', 'enddef'], 'E1055: Missing name after ...')
 enddef
 
 def Test_vim9script_call()
@@ -436,5 +438,28 @@
   CheckDefFailure(['let str: string', 'str = FuncNoArgRetNumber()'], 'E1013: type mismatch, expected string but got number')
 enddef
 
+" When using CheckScriptFailure() for the below test, E1010 is generated instead
+" of E1056.
+func Test_E1056_1059()
+  let caught_1056 = 0
+  try
+    def F():
+      return 1
+    enddef
+  catch /E1056:/
+    let caught_1056 = 1
+  endtry
+  call assert_equal(1, caught_1056)
+
+  let caught_1059 = 0
+  try
+    def F5(items : list)
+      echo 'a'
+    enddef
+  catch /E1059:/
+    let caught_1059 = 1
+  endtry
+  call assert_equal(1, caught_1059)
+endfunc
 
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 01579a8..cab9f86 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -259,7 +259,6 @@
   call CheckDefFailure(['5tab echo 3'], 'E16:')
 enddef
 
-
 def Test_try_catch()
   let l = []
   try
@@ -959,7 +958,6 @@
   assert_true(caught, 'should have caught an exception')
 enddef
 
-
 " Keep this last, it messes up highlighting.
 def Test_substitute_cmd()
   new
diff --git a/src/testdir/test_viminfo.vim b/src/testdir/test_viminfo.vim
index 044da0a..b4708f5 100644
--- a/src/testdir/test_viminfo.vim
+++ b/src/testdir/test_viminfo.vim
@@ -815,3 +815,24 @@
   call test_settime(0)
   let &viminfo=save_viminfo
 endfunc
+
+" Test for errors in setting 'viminfo'
+func Test_viminfo_option_error()
+  " Missing number
+  call assert_fails('set viminfo=\"', 'E526:')
+  for c in split("'/:<@s", '\zs')
+    call assert_fails('set viminfo=' .. c, 'E526:')
+  endfor
+
+  " Missing comma
+  call assert_fails('set viminfo=%10!', 'E527:')
+  call assert_fails('set viminfo=!%10', 'E527:')
+  call assert_fails('set viminfo=h%10', 'E527:')
+  call assert_fails('set viminfo=c%10', 'E527:')
+  call assert_fails('set viminfo=:10%10', 'E527:')
+
+  " Missing ' setting
+  call assert_fails('set viminfo=%10', 'E528:')
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/testdir/test_vimscript.vim b/src/testdir/test_vimscript.vim
index 72eae7c..9bc6702 100644
--- a/src/testdir/test_vimscript.vim
+++ b/src/testdir/test_vimscript.vim
@@ -1998,6 +1998,9 @@
   endtry
   call assert_equal(1, caught_e733)
 
+  " Using endfunc with :if
+  call assert_fails('exe "if 1 | endfunc | endif"', 'E193:')
+
   " Missing 'in' in a :for statement
   call assert_fails('for i range(1) | endfor', 'E690:')
 endfunc
@@ -2044,6 +2047,15 @@
       @a
       let @a = ''
     endfunc
+
+    " Deep nesting of function ... endfunction
+    func Test5()
+      let @a = join(repeat(['function X()'], 51), "\n")
+      let @a ..= "\necho v:true\n"
+      let @a ..= join(repeat(['endfunction'], 51), "\n")
+      @a
+      let @a = ''
+    endfunc
   [SCRIPT]
   call writefile(lines, 'Xscript')
 
@@ -2051,20 +2063,31 @@
 
   " Deep nesting of if ... endif
   call term_sendkeys(buf, ":call Test1()\n")
+  call term_wait(buf)
   call WaitForAssert({-> assert_match('^E579:', term_getline(buf, 5))})
 
   " Deep nesting of for ... endfor
   call term_sendkeys(buf, ":call Test2()\n")
+  call term_wait(buf)
   call WaitForAssert({-> assert_match('^E585:', term_getline(buf, 5))})
 
   " Deep nesting of while ... endwhile
   call term_sendkeys(buf, ":call Test3()\n")
+  call term_wait(buf)
   call WaitForAssert({-> assert_match('^E585:', term_getline(buf, 5))})
 
   " Deep nesting of try ... endtry
   call term_sendkeys(buf, ":call Test4()\n")
+  call term_wait(buf)
   call WaitForAssert({-> assert_match('^E601:', term_getline(buf, 5))})
 
+  " Deep nesting of function ... endfunction
+  call term_sendkeys(buf, ":call Test5()\n")
+  call term_wait(buf)
+  call WaitForAssert({-> assert_match('^E1058:', term_getline(buf, 4))})
+  call term_sendkeys(buf, "\<C-C>\n")
+  call term_wait(buf)
+
   "let l = ''
   "for i in range(1, 6)
   "  let l ..= term_getline(buf, i) . "\n"
diff --git a/src/testdir/test_window_cmd.vim b/src/testdir/test_window_cmd.vim
index 001bbac..a28c00a 100644
--- a/src/testdir/test_window_cmd.vim
+++ b/src/testdir/test_window_cmd.vim
@@ -203,43 +203,6 @@
   %bw!
 endfunc
 
-func Test_window_preview()
-  CheckFeature quickfix
-
-  " Open a preview window
-  pedit Xa
-  call assert_equal(2, winnr('$'))
-  call assert_equal(0, &previewwindow)
-
-  " Go to the preview window
-  wincmd P
-  call assert_equal(1, &previewwindow)
-
-  " Close preview window
-  wincmd z
-  call assert_equal(1, winnr('$'))
-  call assert_equal(0, &previewwindow)
-
-  call assert_fails('wincmd P', 'E441:')
-endfunc
-
-func Test_window_preview_from_help()
-  CheckFeature quickfix
-
-  filetype on
-  call writefile(['/* some C code */'], 'Xpreview.c')
-  help
-  pedit Xpreview.c
-  wincmd P
-  call assert_equal(1, &previewwindow)
-  call assert_equal('c', &filetype)
-  wincmd z
-
-  filetype off
-  close
-  call delete('Xpreview.c')
-endfunc
-
 func Test_window_exchange()
   e Xa