diff --git a/src/testdir/util/check.vim b/src/testdir/util/check.vim
new file mode 100644
index 0000000..aa8eceb
--- /dev/null
+++ b/src/testdir/util/check.vim
@@ -0,0 +1,334 @@
+source util/shared.vim
+source util/term_util.vim
+
+" uses line-continuation
+let s:cpo_save = &cpo
+set cpo&vim
+
+command -nargs=1 MissingFeature throw 'Skipped: ' .. <args> .. ' feature missing'
+
+" Command to check for the presence of a feature.
+command -nargs=1 CheckFeature call CheckFeature(<f-args>)
+func CheckFeature(name)
+  if !has(a:name, 1)
+    throw 'Checking for non-existent feature ' .. a:name
+  endif
+  if !has(a:name)
+    MissingFeature a:name
+  endif
+endfunc
+
+" Command to check for the absence of a feature.
+command -nargs=1 CheckNotFeature call CheckNotFeature(<f-args>)
+func CheckNotFeature(name)
+  if !has(a:name, 1)
+    throw 'Checking for non-existent feature ' .. a:name
+  endif
+  if has(a:name)
+    throw 'Skipped: ' .. a:name .. ' feature present'
+  endif
+endfunc
+
+" Command to check for the presence of a working option.
+command -nargs=1 CheckOption call CheckOption(<f-args>)
+func CheckOption(name)
+  if !exists('&' .. a:name)
+    throw 'Checking for non-existent option ' .. a:name
+  endif
+  if !exists('+' .. a:name)
+    throw 'Skipped: ' .. a:name .. ' option not supported'
+  endif
+endfunc
+
+" Command to check for the presence of a built-in function.
+command -nargs=1 CheckFunction call CheckFunction(<f-args>)
+func CheckFunction(name)
+  if !exists('?' .. a:name)
+    throw 'Checking for non-existent function ' .. a:name
+  endif
+  if !exists('*' .. a:name)
+    throw 'Skipped: ' .. a:name .. ' function missing'
+  endif
+endfunc
+
+" Command to check for the presence of an Ex command
+command -nargs=1 CheckCommand call CheckCommand(<f-args>)
+func CheckCommand(name)
+  if !exists(':' .. a:name)
+    throw 'Skipped: ' .. a:name .. ' command not supported'
+  endif
+endfunc
+
+" Command to check for the presence of a shell command
+command -nargs=1 CheckExecutable call CheckExecutable(<f-args>)
+func CheckExecutable(name)
+  if !executable(a:name)
+    throw 'Skipped: ' .. a:name .. ' program not executable'
+  endif
+endfunc
+
+" Command to check for the presence of python.  Argument should have been
+" obtained with PythonProg()
+func CheckPython(name)
+  if a:name == ''
+    throw 'Skipped: python command not available'
+  endif
+endfunc
+
+" Command to check for running on MS-Windows
+command CheckMSWindows call CheckMSWindows()
+func CheckMSWindows()
+  if !has('win32')
+    throw 'Skipped: only works on MS-Windows'
+  endif
+endfunc
+
+" Command to check for NOT running on MS-Windows
+command CheckNotMSWindows call CheckNotMSWindows()
+func CheckNotMSWindows()
+  if has('win32')
+    throw 'Skipped: does not work on MS-Windows'
+  endif
+endfunc
+
+" Command to check for running on Unix
+command CheckUnix call CheckUnix()
+func CheckUnix()
+  if !has('unix')
+    throw 'Skipped: only works on Unix'
+  endif
+endfunc
+
+" Command to check for running on Linux
+command CheckLinux call CheckLinux()
+func CheckLinux()
+  if !has('linux')
+    throw 'Skipped: only works on Linux'
+  endif
+endfunc
+
+" Command to check for not running on a BSD system.
+command CheckNotBSD call CheckNotBSD()
+func CheckNotBSD()
+  if has('bsd')
+    throw 'Skipped: does not work on BSD'
+  endif
+endfunc
+
+" Command to check for not running on a MacOS
+command CheckNotMac call CheckNotMac()
+func CheckNotMac()
+  if has('mac')
+    throw 'Skipped: does not work on MacOS'
+  endif
+endfunc
+
+" Command to check for not running on a MacOS M1 system.
+command CheckNotMacM1 call CheckNotMacM1()
+func CheckNotMacM1()
+  if has('mac') && system('uname -a') =~ '\<arm64\>'
+    throw 'Skipped: does not work on MacOS M1'
+  endif
+endfunc
+
+func SetupWindowSizeToForVisualDumps()
+  " The dumps used as reference in these tests were created with a terminal
+  " width of 75 columns. The vim window that uses the remainder of the GUI
+  " window width must be at least 3 columns. In theory this means we need the
+  " GUI shell to provide 78+ columns. However the GTK3 resize logic is flaky,
+  " sometimes resulting in X11 Configure events that are narrower than
+  " expected by a number of pixels equal to 2 column widths. Therefore
+  " setting 80 columns ensures that the GUI shell can still provide 78+
+  " columns. This is very likely papering over a GTK3 resize bug but one that
+  " has existed for a very long time. Establishing this workaround is meant to
+  " get the GTK3 code working under CI so that we can focus on removing this
+  " over the long term.
+  if &columns != 80
+    set columns=80
+  endif
+  " Without resetting lines, some GTK3 resize events can carry over between
+  " tests, which invalidate assumptions in the scrollbar offset calculations.
+  if &lines != 25
+    set lines=25
+  endif
+endfunc
+
+" Command to check that making screendumps is supported.
+" Caller must source util/screendump.vim
+command CheckScreendump call CheckScreendump()
+func CheckScreendump()
+  let g:check_screendump_called = v:true
+  if !CanRunVimInTerminal()
+    throw 'Skipped: cannot make screendumps'
+  endif
+  if has('gui_running')
+    call SetupWindowSizeToForVisualDumps()
+  endif
+endfunc
+
+" Command to check that we can Run Vim in a terminal window
+command CheckRunVimInTerminal call CheckRunVimInTerminal()
+func CheckRunVimInTerminal()
+  if !CanRunVimInTerminal()
+    throw 'Skipped: cannot run Vim in a terminal window'
+  endif
+endfunc
+
+" Command to check that we can run the GUI
+command CheckCanRunGui call CheckCanRunGui()
+func CheckCanRunGui()
+  if !has('gui') || ($DISPLAY == "" && !has('gui_running'))
+    throw 'Skipped: cannot start the GUI'
+  endif
+endfunc
+
+" Command to Check for an environment variable
+command -nargs=1 CheckEnv call CheckEnv(<f-args>)
+func CheckEnv(name)
+  if empty(eval('$' .. a:name))
+    throw 'Skipped: Environment variable ' .. a:name .. ' is not set'
+  endif
+endfunc
+
+" Command to Check for pure X11 (no Wayland)
+command -nargs=0 CheckX11 call CheckX11()
+func CheckX11()
+  if !empty($WAYLAND_DISPLAY) || empty($DISPLAY)
+    throw 'Skipped: not pure X11 environment'
+  endif
+endfunc
+
+" Command to check that we are using the GUI
+command CheckGui call CheckGui()
+func CheckGui()
+  if !has('gui_running')
+    throw 'Skipped: only works in the GUI'
+  endif
+endfunc
+
+" Command to check that not currently using the GUI
+command CheckNotGui call CheckNotGui()
+func CheckNotGui()
+  if has('gui_running')
+    throw 'Skipped: only works in the terminal'
+  endif
+endfunc
+
+" Command to check that test is not running as root
+command CheckNotRoot call CheckNotRoot()
+func CheckNotRoot()
+  if IsRoot()
+    throw 'Skipped: cannot run test as root'
+  endif
+endfunc
+
+" Command to check that the current language is English
+command CheckEnglish call CheckEnglish()
+func CheckEnglish()
+  if v:lang != "C" && v:lang !~ '^[Ee]n'
+      throw 'Skipped: only works in English language environment'
+  endif
+endfunc
+
+" Command to check that loopback device has IPv6 address
+command CheckIPv6 call CheckIPv6()
+func CheckIPv6()
+  if !has('ipv6')
+    throw 'Skipped: cannot use IPv6 networking'
+  endif
+  if !exists('s:ipv6_loopback')
+    let s:ipv6_loopback = s:CheckIPv6Loopback()
+  endif
+  if !s:ipv6_loopback
+    throw 'Skipped: no IPv6 address for loopback device'
+  endif
+endfunc
+
+func s:CheckIPv6Loopback()
+  if has('win32')
+    return system('netsh interface ipv6 show interface') =~? '\<Loopback\>'
+  elseif filereadable('/proc/net/if_inet6')
+    return (match(readfile('/proc/net/if_inet6'), '\slo$') >= 0)
+  elseif executable('ifconfig')
+    for dev in ['lo0', 'lo', 'loop']
+      " NOTE: On SunOS, need specify address family 'inet6' to get IPv6 info.
+      if system('ifconfig ' .. dev .. ' inet6 2>/dev/null') =~? '\<inet6\>'
+            \ || system('ifconfig ' .. dev .. ' 2>/dev/null') =~? '\<inet6\>'
+        return v:true
+      endif
+    endfor
+  else
+    " TODO: How to check it in other platforms?
+  endif
+  return v:false
+endfunc
+
+" Command to check for not running under ASAN
+command CheckNotAsan call CheckNotAsan()
+func CheckNotAsan()
+  if execute('version') =~# '-fsanitize=[a-z,]*\<address\>'
+    throw 'Skipped: does not work with ASAN'
+  endif
+endfunc
+
+" Command to check for not running under valgrind
+command CheckNotValgrind call CheckNotValgrind()
+func CheckNotValgrind()
+  if RunningWithValgrind()
+    throw 'Skipped: does not work well with valgrind'
+  endif
+endfunc
+
+" Command to check for X11 based GUI
+command CheckX11BasedGui call CheckX11BasedGui()
+func CheckX11BasedGui()
+  if !g:x11_based_gui
+    throw 'Skipped: requires X11 based GUI'
+  endif
+endfunc
+
+" Command to check that there are two clipboards
+command CheckTwoClipboards call CheckTwoClipboards()
+func CheckTwoClipboards()
+  " avoid changing the clipboard here, only X11 supports both
+  if !has('X11')
+    throw 'Skipped: requires two clipboards'
+  endif
+endfunc
+
+" Command to check for satisfying any of the conditions.
+" e.g. CheckAnyOf Feature:bsd Feature:sun Linux
+command -nargs=+ CheckAnyOf call CheckAnyOf(<f-args>)
+func CheckAnyOf(...)
+  let excp = []
+  for arg in a:000
+    try
+      exe 'Check' .. substitute(arg, ':', ' ', '')
+      return
+    catch /^Skipped:/
+      let excp += [substitute(v:exception, '^Skipped:\s*', '', '')]
+    endtry
+  endfor
+  throw 'Skipped: ' .. join(excp, '; ')
+endfunc
+
+" Command to check for satisfying all of the conditions.
+" e.g. CheckAllOf Unix Gui Option:ballooneval
+command -nargs=+ CheckAllOf call CheckAllOf(<f-args>)
+func CheckAllOf(...)
+  for arg in a:000
+    exe 'Check' .. substitute(arg, ':', ' ', '')
+  endfor
+endfunc
+
+" Check if running under Github Actions
+command CheckGithubActions call CheckGithubActions()
+func CheckGithubActions()
+  if expand('$GITHUB_ACTIONS') ==# 'true'
+    throw "Skipped: FIXME: this test doesn't work on Github Actions CI"
+  endif
+endfunc
+
+let &cpo = s:cpo_save
+unlet s:cpo_save
+" vim: shiftwidth=2 sts=2 expandtab