diff --git a/CMakeLists.txt b/CMakeLists.txt
index dad0093cf0..9502190708 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -678,7 +678,7 @@ if(BUSTED_PRG)
   list(APPEND TEST_TARGET_ARGS "USES_TERMINAL")
 
   set(UNITTEST_PREREQS nvim-test unittest-headers)
-  set(FUNCTIONALTEST_PREREQS nvim printenv-test printargs-test shell-test streams-test tty-test ${GENERATED_HELP_TAGS})
+  set(FUNCTIONALTEST_PREREQS nvim printenv-test printargs-test shell-test pwsh-test streams-test tty-test ${GENERATED_HELP_TAGS})
   set(BENCHMARK_PREREQS nvim tty-test)
 
   check_lua_module(${LUA_PRG} "ffi" LUA_HAS_FFI)
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 0f351d8af6..bd8c099579 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -1579,11 +1579,11 @@ char *make_filter_cmd(char *cmd, char *itmp, char *otmp)
   size_t len = STRLEN(cmd) + 1;  // At least enough space for cmd + NULL.
 
   len += is_fish_shell ?  sizeof("begin; " "; end") - 1
-                       :  is_pwsh ? STRLEN("Start-Process ")
+                       :  is_pwsh ? sizeof("Start-Process ")
                                   : sizeof("(" ")") - 1;
 
   if (itmp != NULL) {
-    len += is_pwsh  ? STRLEN(itmp) + STRLEN(" -RedirectStandardInput ")
+    len += is_pwsh  ? STRLEN(itmp) + sizeof(" -RedirectStandardInput ")
                     : STRLEN(itmp) + sizeof(" { " " < " " } ") - 1;
   }
   if (otmp != NULL) {
@@ -1596,7 +1596,7 @@ char *make_filter_cmd(char *cmd, char *itmp, char *otmp)
   // redirecting input and/or output.
   if (is_pwsh) {
     xstrlcpy(buf, "Start-Process ", len);
-    xstrlcat(buf, (char *)cmd, len);
+    xstrlcat(buf, cmd, len);
   } else if (itmp != NULL || otmp != NULL) {
     char *fmt = is_fish_shell ? "begin; %s; end"
                               :       "(%s)";
@@ -1611,16 +1611,16 @@ char *make_filter_cmd(char *cmd, char *itmp, char *otmp)
     } else {
       xstrlcat(buf, " < ", len - 1);
     }
-    xstrlcat(buf, (const char *)itmp, len - 1);
+    xstrlcat(buf, itmp, len - 1);
   }
 #else
   // For shells that don't understand braces around commands, at least allow
   // the use of commands in a pipe.
   if (is_pwsh) {
     xstrlcpy(buf, "Start-Process ", len);
-    xstrlcat(buf, (char *)cmd, len);
+    xstrlcat(buf, cmd, len);
   } else {
-    xstrlcpy(buf, (char *)cmd, len);
+    xstrlcpy(buf, cmd, len);
   }
   if (itmp != NULL) {
     // If there is a pipe, we have to put the '<' in front of it.
@@ -1637,9 +1637,9 @@ char *make_filter_cmd(char *cmd, char *itmp, char *otmp)
     } else {
       xstrlcat(buf, " < ", len);
     }
-    xstrlcat(buf, (const char *)itmp, len);
+    xstrlcat(buf, itmp, len);
     if (*p_shq == NUL) {
-      const char *const p = find_pipe((const char *)cmd);
+      const char *const p = find_pipe(cmd);
       if (p != NULL) {
         xstrlcat(buf, " ", len - 1);  // Insert a space before the '|' for DOS
         xstrlcat(buf, p, len - 1);
diff --git a/test/functional/autocmd/termxx_spec.lua b/test/functional/autocmd/termxx_spec.lua
index 1e8f981437..c418a12faf 100644
--- a/test/functional/autocmd/termxx_spec.lua
+++ b/test/functional/autocmd/termxx_spec.lua
@@ -1,8 +1,8 @@
 local luv = require('luv')
 local helpers = require('test.functional.helpers')(after_each)
 
-local clear, command, nvim, nvim_dir =
-  helpers.clear, helpers.command, helpers.nvim, helpers.nvim_dir
+local clear, command, nvim, testprg =
+  helpers.clear, helpers.command, helpers.nvim, helpers.testprg
 local eval, eq, neq, retry =
   helpers.eval, helpers.eq, helpers.neq, helpers.retry
 local ok = helpers.ok
@@ -12,7 +12,7 @@ local iswin = helpers.iswin
 describe('autocmd TermClose', function()
   before_each(function()
     clear()
-    nvim('set_option', 'shell', nvim_dir .. '/shell-test')
+    nvim('set_option', 'shell', testprg('shell-test'))
     command('set shellcmdflag=EXE shellredir= shellpipe= shellquote= shellxquote=')
   end)
 
diff --git a/test/functional/core/job_spec.lua b/test/functional/core/job_spec.lua
index 461a69f357..a6763ba3c7 100644
--- a/test/functional/core/job_spec.lua
+++ b/test/functional/core/job_spec.lua
@@ -1,9 +1,9 @@
 local helpers = require('test.functional.helpers')(after_each)
 local clear, eq, eval, exc_exec, feed_command, feed, insert, neq, next_msg, nvim,
-  nvim_dir, ok, source, write_file, mkdir, rmdir = helpers.clear,
+  testprg, ok, source, write_file, mkdir, rmdir = helpers.clear,
   helpers.eq, helpers.eval, helpers.exc_exec, helpers.feed_command, helpers.feed,
   helpers.insert, helpers.neq, helpers.next_msg, helpers.nvim,
-  helpers.nvim_dir, helpers.ok, helpers.source,
+  helpers.testprg, helpers.ok, helpers.source,
   helpers.write_file, helpers.mkdir, helpers.rmdir
 local assert_alive = helpers.assert_alive
 local command = helpers.command
@@ -1043,8 +1043,7 @@ describe('jobs', function()
         return a:data
       endfunction
       ]])
-      local ext = iswin() and '.exe' or ''
-      insert(nvim_dir..'/tty-test'..ext)  -- Full path to tty-test.
+      insert(testprg('tty-test'))
       nvim('command', 'let g:job_opts.pty = 1')
       nvim('command', 'let exec = [expand("<cfile>:p")]')
       nvim('command', "let j = jobstart(exec, g:job_opts)")
diff --git a/test/functional/ex_cmds/ls_spec.lua b/test/functional/ex_cmds/ls_spec.lua
index 9853084c47..2583d80269 100644
--- a/test/functional/ex_cmds/ls_spec.lua
+++ b/test/functional/ex_cmds/ls_spec.lua
@@ -5,7 +5,7 @@ local eq = helpers.eq
 local eval = helpers.eval
 local feed = helpers.feed
 local nvim = helpers.nvim
-local nvim_dir = helpers.nvim_dir
+local testprg = helpers.testprg
 local retry = helpers.retry
 
 describe(':ls', function()
@@ -14,7 +14,7 @@ describe(':ls', function()
   end)
 
   it('R, F for :terminal buffers', function()
-    nvim('set_option', 'shell', string.format('"%s" INTERACT', nvim_dir..'/shell-test'))
+    nvim('set_option', 'shell', string.format('"%s" INTERACT', testprg('shell-test')))
 
     command('edit foo')
     command('set hidden')
diff --git a/test/functional/ex_cmds/make_spec.lua b/test/functional/ex_cmds/make_spec.lua
index 3b4d22ab38..bf585ee44c 100644
--- a/test/functional/ex_cmds/make_spec.lua
+++ b/test/functional/ex_cmds/make_spec.lua
@@ -4,7 +4,7 @@ local eval = helpers.eval
 local has_powershell = helpers.has_powershell
 local matches = helpers.matches
 local nvim = helpers.nvim
-local nvim_dir = helpers.nvim_dir
+local testprg = helpers.testprg
 
 describe(':make', function()
   clear()
@@ -22,7 +22,7 @@ describe(':make', function()
     end)
 
     it('captures stderr & non zero exit code #14349', function ()
-      nvim('set_option', 'makeprg', nvim_dir..'/shell-test foo')
+      nvim('set_option', 'makeprg', testprg('shell-test')..' foo')
       local out = eval('execute("make")')
       -- Make program exit code correctly captured
       matches('\nshell returned 3', out)
@@ -31,7 +31,7 @@ describe(':make', function()
     end)
 
     it('captures stderr & zero exit code #14349', function ()
-      nvim('set_option', 'makeprg', nvim_dir..'/shell-test')
+      nvim('set_option', 'makeprg', testprg('shell-test'))
       local out = eval('execute("make")')
       -- Ensure there are no "shell returned X" messages between
 	  -- command and last line (indicating zero exit)
diff --git a/test/functional/fixtures/CMakeLists.txt b/test/functional/fixtures/CMakeLists.txt
index 6010fcaf1e..a5410c2f8c 100644
--- a/test/functional/fixtures/CMakeLists.txt
+++ b/test/functional/fixtures/CMakeLists.txt
@@ -2,6 +2,8 @@ add_executable(tty-test EXCLUDE_FROM_ALL tty-test.c)
 target_link_libraries(tty-test ${LIBUV_LIBRARIES})
 
 add_executable(shell-test EXCLUDE_FROM_ALL shell-test.c)
+# Fake pwsh (powershell) for testing make_filter_cmd(). #16271
+add_executable(pwsh-test EXCLUDE_FROM_ALL shell-test.c)
 add_executable(printargs-test EXCLUDE_FROM_ALL printargs-test.c)
 add_executable(printenv-test EXCLUDE_FROM_ALL printenv-test.c)
 if(MINGW)
diff --git a/test/functional/helpers.lua b/test/functional/helpers.lua
index 2018f80052..0c616e73fb 100644
--- a/test/functional/helpers.lua
+++ b/test/functional/helpers.lua
@@ -515,9 +515,17 @@ function module.has_powershell()
   return module.eval('executable("'..(iswin() and 'powershell' or 'pwsh')..'")') == 1
 end
 
-function module.set_shell_powershell()
-  local shell = iswin() and 'powershell' or 'pwsh'
-  assert(module.has_powershell())
+--- Sets Nvim shell to powershell.
+---
+--- @param fake (boolean) If true, a fake will be used if powershell is not
+---             found on the system.
+--- @returns true if powershell was found on the system, else false.
+function module.set_shell_powershell(fake)
+  local found = module.has_powershell()
+  if not fake then
+    assert(found)
+  end
+  local shell = found and (iswin() and 'powershell' or 'pwsh') or module.testprg('pwsh-test')
   local set_encoding = '[Console]::InputEncoding=[Console]::OutputEncoding=[System.Text.Encoding]::UTF8;'
   local cmd = set_encoding..'Remove-Item -Force '..table.concat(iswin()
     and {'alias:cat', 'alias:echo', 'alias:sleep'}
@@ -529,6 +537,7 @@ function module.set_shell_powershell()
     let &shellpipe = '2>&1 | Out-File -Encoding UTF8 %s; exit $LastExitCode'
     let &shellredir = '-RedirectStandardOutput %s -NoNewWindow -Wait'
   ]])
+  return found
 end
 
 function module.nvim(method, ...)
@@ -784,11 +793,21 @@ function module.get_pathsep()
   return iswin() and '\\' or '/'
 end
 
+--- Gets the filesystem root dir, namely "/" or "C:/".
 function module.pathroot()
   local pathsep = package.config:sub(1,1)
   return iswin() and (module.nvim_dir:sub(1,2)..pathsep) or '/'
 end
 
+--- Gets the full `…/build/bin/{name}` path of a test program produced by
+--- `test/functional/fixtures/CMakeLists.txt`.
+---
+--- @param name (string) Name of the test program.
+function module.testprg(name)
+  local ext = module.iswin() and '.exe' or ''
+  return ('%s/%s%s'):format(module.nvim_dir, name, ext)
+end
+
 -- Returns a valid, platform-independent Nvim listen address.
 -- Useful for communicating with child instances.
 function module.new_pipename()
diff --git a/test/functional/terminal/cursor_spec.lua b/test/functional/terminal/cursor_spec.lua
index 6e06304acd..2d1c790d2f 100644
--- a/test/functional/terminal/cursor_spec.lua
+++ b/test/functional/terminal/cursor_spec.lua
@@ -2,7 +2,7 @@ local helpers = require('test.functional.helpers')(after_each)
 local Screen = require('test.functional.ui.screen')
 local thelpers = require('test.functional.terminal.helpers')
 local feed, clear, nvim = helpers.feed, helpers.clear, helpers.nvim
-local nvim_dir, command = helpers.nvim_dir, helpers.command
+local testprg, command = helpers.testprg, helpers.command
 local nvim_prog = helpers.nvim_prog
 local eq, eval = helpers.eq, helpers.eval
 local matches = helpers.matches
@@ -150,7 +150,7 @@ describe('cursor with customized highlighting', function()
       [3] = {bold = true},
     })
     screen:attach({rgb=false})
-    command('call termopen(["'..nvim_dir..'/tty-test"])')
+    command('call termopen(["'..testprg('tty-test')..'"])')
     feed_command('startinsert')
   end)
 
diff --git a/test/functional/terminal/edit_spec.lua b/test/functional/terminal/edit_spec.lua
index e7025d6739..aeb4b7cc2e 100644
--- a/test/functional/terminal/edit_spec.lua
+++ b/test/functional/terminal/edit_spec.lua
@@ -3,7 +3,7 @@ local screen = require('test.functional.ui.screen')
 
 local curbufmeths = helpers.curbufmeths
 local curwinmeths = helpers.curwinmeths
-local nvim_dir = helpers.nvim_dir
+local testprg = helpers.testprg
 local command = helpers.command
 local funcs = helpers.funcs
 local meths = helpers.meths
@@ -21,7 +21,7 @@ describe(':edit term://*', function()
 
   before_each(function()
     clear()
-    meths.set_option('shell', nvim_dir .. '/shell-test')
+    meths.set_option('shell', testprg('shell-test'))
     meths.set_option('shellcmdflag', 'EXE')
   end)
 
diff --git a/test/functional/terminal/ex_terminal_spec.lua b/test/functional/terminal/ex_terminal_spec.lua
index b4f29a586a..23b69319f0 100644
--- a/test/functional/terminal/ex_terminal_spec.lua
+++ b/test/functional/terminal/ex_terminal_spec.lua
@@ -2,7 +2,7 @@ local helpers = require('test.functional.helpers')(after_each)
 local Screen = require('test.functional.ui.screen')
 local assert_alive = helpers.assert_alive
 local clear, poke_eventloop, nvim = helpers.clear, helpers.poke_eventloop, helpers.nvim
-local nvim_dir, source, eq = helpers.nvim_dir, helpers.source, helpers.eq
+local testprg, source, eq = helpers.testprg, helpers.source, helpers.eq
 local feed = helpers.feed
 local feed_command, eval = helpers.feed_command, helpers.eval
 local funcs = helpers.funcs
@@ -28,7 +28,7 @@ describe(':terminal', function()
       echomsg "msg3"
     ]])
     -- Invoke a command that emits frequent terminal activity.
-    feed([[:terminal "]]..nvim_dir..[[/shell-test" REP 9999 !terminal_output!<cr>]])
+    feed([[:terminal "]]..testprg('shell-test')..[[" REP 9999 !terminal_output!<cr>]])
     feed([[<C-\><C-N>]])
     poke_eventloop()
     -- Wait for some terminal activity.
@@ -131,7 +131,7 @@ describe(':terminal (with fake shell)', function()
     screen = Screen.new(50, 4)
     screen:attach({rgb=false})
     -- shell-test.c is a fake shell that prints its arguments and exits.
-    nvim('set_option', 'shell', nvim_dir..'/shell-test')
+    nvim('set_option', 'shell', testprg('shell-test'))
     nvim('set_option', 'shellcmdflag', 'EXE')
   end)
 
@@ -167,7 +167,7 @@ describe(':terminal (with fake shell)', function()
 
   it("with no argument, but 'shell' has arguments, acts like termopen()", function()
     if helpers.pending_win32(pending) then return end
-    nvim('set_option', 'shell', nvim_dir..'/shell-test -t jeff')
+    nvim('set_option', 'shell', testprg('shell-test')..' -t jeff')
     terminal_with_fake_shell()
     screen:expect([[
       ^jeff $                                            |
@@ -191,7 +191,7 @@ describe(':terminal (with fake shell)', function()
 
   it("executes a given command through the shell, when 'shell' has arguments", function()
     if helpers.pending_win32(pending) then return end
-    nvim('set_option', 'shell', nvim_dir..'/shell-test -t jeff')
+    nvim('set_option', 'shell', testprg('shell-test')..' -t jeff')
     command('set shellxquote=')   -- win: avoid extra quotes
     terminal_with_fake_shell('echo hi')
     screen:expect([[
diff --git a/test/functional/terminal/helpers.lua b/test/functional/terminal/helpers.lua
index 51ecae663a..bcfd3559e6 100644
--- a/test/functional/terminal/helpers.lua
+++ b/test/functional/terminal/helpers.lua
@@ -3,7 +3,7 @@
 -- operate on the _host_ session, _not_ the child session.
 local helpers = require('test.functional.helpers')(nil)
 local Screen = require('test.functional.ui.screen')
-local nvim_dir = helpers.nvim_dir
+local testprg = helpers.testprg
 local feed_command, nvim = helpers.feed_command, helpers.nvim
 
 local function feed_data(data)
@@ -37,7 +37,7 @@ local function clear_attrs() feed_termcode('[0;10m') end
 local function enable_mouse() feed_termcode('[?1002h') end
 local function disable_mouse() feed_termcode('[?1002l') end
 
-local default_command = '["'..nvim_dir..'/tty-test'..'"]'
+local default_command = '["'..testprg('tty-test')..'"]'
 
 local function screen_setup(extra_rows, command, cols, opts)
   extra_rows = extra_rows and extra_rows or 0
diff --git a/test/functional/terminal/highlight_spec.lua b/test/functional/terminal/highlight_spec.lua
index 2a63971d48..1eb7223dce 100644
--- a/test/functional/terminal/highlight_spec.lua
+++ b/test/functional/terminal/highlight_spec.lua
@@ -2,7 +2,7 @@ local helpers = require('test.functional.helpers')(after_each)
 local Screen = require('test.functional.ui.screen')
 local thelpers = require('test.functional.terminal.helpers')
 local feed, clear, nvim = helpers.feed, helpers.clear, helpers.nvim
-local nvim_dir, command = helpers.nvim_dir, helpers.command
+local testprg, command = helpers.testprg, helpers.command
 local nvim_prog_abs = helpers.nvim_prog_abs
 local eq, eval = helpers.eq, helpers.eval
 local funcs = helpers.funcs
@@ -28,7 +28,7 @@ describe(':terminal highlight', function()
       [11] = {background = 11},
     })
     screen:attach({rgb=false})
-    command('enew | call termopen(["'..nvim_dir..'/tty-test"])')
+    command(("enew | call termopen(['%s'])"):format(testprg('tty-test')))
     feed('i')
     screen:expect([[
       tty ready                                         |
@@ -173,7 +173,7 @@ describe(':terminal highlight forwarding', function()
       [4] = {{foreground = tonumber('0xff8000')}, {}},
     })
     screen:attach()
-    command('enew | call termopen(["'..nvim_dir..'/tty-test"])')
+    command(("enew | call termopen(['%s'])"):format(testprg('tty-test')))
     feed('i')
     screen:expect([[
       tty ready                                         |
@@ -225,7 +225,7 @@ describe(':terminal highlight with custom palette', function()
     })
     screen:attach({rgb=true})
     nvim('set_var', 'terminal_color_3', '#123456')
-    command('enew | call termopen(["'..nvim_dir..'/tty-test"])')
+    command(("enew | call termopen(['%s'])"):format(testprg('tty-test')))
     feed('i')
     screen:expect([[
       tty ready                                         |
diff --git a/test/functional/terminal/scrollback_spec.lua b/test/functional/terminal/scrollback_spec.lua
index b1d3b502b2..b491cb2735 100644
--- a/test/functional/terminal/scrollback_spec.lua
+++ b/test/functional/terminal/scrollback_spec.lua
@@ -2,7 +2,7 @@ local Screen = require('test.functional.ui.screen')
 local helpers = require('test.functional.helpers')(after_each)
 local thelpers = require('test.functional.terminal.helpers')
 local clear, eq, curbuf = helpers.clear, helpers.eq, helpers.curbuf
-local feed, nvim_dir, feed_command = helpers.feed, helpers.nvim_dir, helpers.feed_command
+local feed, testprg, feed_command = helpers.feed, helpers.testprg, helpers.feed_command
 local iswin = helpers.iswin
 local eval = helpers.eval
 local command = helpers.command
@@ -350,7 +350,7 @@ describe(':terminal prints more lines than the screen height and exits', functio
     clear()
     local screen = Screen.new(30, 7)
     screen:attach({rgb=false})
-    feed_command('call termopen(["'..nvim_dir..'/tty-test", "10"]) | startinsert')
+    feed_command(("call termopen(['%s', '10']) | startinsert"):format(testprg('tty-test')))
     poke_eventloop()
     screen:expect([[
       line6                         |
@@ -382,7 +382,7 @@ describe("'scrollback' option", function()
 
   local function set_fake_shell()
     -- shell-test.c is a fake shell that prints its arguments and exits.
-    nvim('set_option', 'shell', nvim_dir..'/shell-test')
+    nvim('set_option', 'shell', testprg('shell-test'))
     nvim('set_option', 'shellcmdflag', 'EXE')
   end
 
@@ -403,7 +403,7 @@ describe("'scrollback' option", function()
     end
 
     curbufmeths.set_option('scrollback', 0)
-    feed_data(nvim_dir..'/shell-test REP 31 line'..(iswin() and '\r' or '\n'))
+    feed_data(('%s REP 31 line%s'):format(testprg('shell-test'), iswin() and '\r' or '\n'))
     screen:expect{any='30: line                      '}
     retry(nil, nil, function() expect_lines(7) end)
   end)
@@ -423,7 +423,7 @@ describe("'scrollback' option", function()
     -- Wait for prompt.
     screen:expect{any='%$'}
 
-    feed_data(nvim_dir.."/shell-test REP 31 line"..(iswin() and '\r' or '\n'))
+    feed_data(('%s REP 31 line%s'):format(testprg('shell-test'), iswin() and '\r' or '\n'))
     screen:expect{any='30: line                      '}
 
     retry(nil, nil, function() expect_lines(33, 2) end)
@@ -436,7 +436,7 @@ describe("'scrollback' option", function()
     -- 'scrollback' option is synchronized with the internal sb_buffer.
     command('sleep 100m')
 
-    feed_data(nvim_dir.."/shell-test REP 41 line"..(iswin() and '\r' or '\n'))
+    feed_data(('%s REP 41 line%s'):format(testprg('shell-test'), iswin() and '\r' or '\n'))
     if iswin() then
       screen:expect{grid=[[
         37: line                      |
diff --git a/test/functional/terminal/tui_spec.lua b/test/functional/terminal/tui_spec.lua
index 8c6cba4def..89704be820 100644
--- a/test/functional/terminal/tui_spec.lua
+++ b/test/functional/terminal/tui_spec.lua
@@ -14,7 +14,7 @@ local feed_command = helpers.feed_command
 local feed_data = thelpers.feed_data
 local clear = helpers.clear
 local command = helpers.command
-local nvim_dir = helpers.nvim_dir
+local testprg = helpers.testprg
 local retry = helpers.retry
 local nvim_prog = helpers.nvim_prog
 local nvim_set = helpers.nvim_set
@@ -385,7 +385,7 @@ describe('TUI', function()
         return
     end
     feed_data(':set statusline=^^^^^^^\n')
-    feed_data(':terminal '..nvim_dir..'/tty-test\n')
+    feed_data(':terminal '..testprg('tty-test')..'\n')
     feed_data('i')
     screen:expect{grid=[[
       tty ready                                         |
@@ -903,7 +903,7 @@ describe('TUI', function()
 
     feed_data(':set statusline=^^^^^^^\n')
     feed_data(':set termguicolors\n')
-    feed_data(':terminal '..nvim_dir..'/tty-test\n')
+    feed_data(':terminal '..testprg('tty-test')..'\n')
     -- Depending on platform the above might or might not fit in the cmdline
     -- so clear it for consistent behavior.
     feed_data(':\027')
@@ -1130,7 +1130,7 @@ describe('TUI FocusGained/FocusLost', function()
   end)
 
   it('in terminal-mode', function()
-    feed_data(':set shell='..nvim_dir..'/shell-test\n')
+    feed_data(':set shell='..testprg('shell-test')..'\n')
     feed_data(':set noshowmode laststatus=0\n')
 
     feed_data(':terminal\n')
diff --git a/test/functional/ui/hlstate_spec.lua b/test/functional/ui/hlstate_spec.lua
index 925af11627..df7f34aa7f 100644
--- a/test/functional/ui/hlstate_spec.lua
+++ b/test/functional/ui/hlstate_spec.lua
@@ -5,7 +5,7 @@ local clear, insert = helpers.clear, helpers.insert
 local command = helpers.command
 local meths = helpers.meths
 local iswin = helpers.iswin
-local nvim_dir = helpers.nvim_dir
+local testprg = helpers.testprg
 local thelpers = require('test.functional.terminal.helpers')
 
 describe('ext_hlstate detailed highlights', function()
@@ -191,7 +191,7 @@ describe('ext_hlstate detailed highlights', function()
       [6] = {{foreground = tonumber('0x40ffff'), fg_indexed=true}, {5, 1}},
       [7] = {{}, {{hi_name = "MsgArea", ui_name = "MsgArea", kind = "ui"}}},
     })
-    command('enew | call termopen(["'..nvim_dir..'/tty-test"])')
+    command(("enew | call termopen(['%s'])"):format(testprg('tty-test')))
     screen:expect([[
       ^tty ready                               |
       {1: }                                       |
diff --git a/test/functional/ui/inccommand_spec.lua b/test/functional/ui/inccommand_spec.lua
index 98ed564966..7a42e72732 100644
--- a/test/functional/ui/inccommand_spec.lua
+++ b/test/functional/ui/inccommand_spec.lua
@@ -17,7 +17,7 @@ local source = helpers.source
 local poke_eventloop = helpers.poke_eventloop
 local nvim = helpers.nvim
 local sleep = helpers.sleep
-local nvim_dir = helpers.nvim_dir
+local testprg = helpers.testprg
 local assert_alive = helpers.assert_alive
 
 local default_text = [[
@@ -2875,7 +2875,7 @@ it(':substitute with inccommand during :terminal activity', function()
     clear()
 
     command("set cmdwinheight=3")
-    feed([[:terminal "]]..nvim_dir..[[/shell-test" REP 5000 xxx<cr>]])
+    feed(([[:terminal "%s" REP 5000 xxx<cr>]]):format(testprg('shell-test')))
     command('file term')
     feed('G')  -- Follow :terminal output.
     command('new')
diff --git a/test/functional/ui/output_spec.lua b/test/functional/ui/output_spec.lua
index 50e5dfac84..71c6410013 100644
--- a/test/functional/ui/output_spec.lua
+++ b/test/functional/ui/output_spec.lua
@@ -9,6 +9,7 @@ local feed_command = helpers.feed_command
 local iswin = helpers.iswin
 local clear = helpers.clear
 local command = helpers.command
+local testprg = helpers.testprg
 local nvim_dir = helpers.nvim_dir
 local has_powershell = helpers.has_powershell
 local set_shell_powershell = helpers.set_shell_powershell
@@ -54,7 +55,7 @@ describe("shell command :!", function()
     if 'openbsd' == helpers.uname() then
       pending('FIXME #10804')
     end
-    child_session.feed_data(":!"..nvim_dir.."/shell-test REP 30001 foo\n")
+    child_session.feed_data((":!%s REP 30001 foo\n"):format(testprg('shell-test')))
 
     -- If we observe any line starting with a dot, then throttling occurred.
     -- Avoid false failure on slow systems.
@@ -207,12 +208,7 @@ describe("shell command :!", function()
 
     it('handles multibyte sequences split over buffer boundaries', function()
       command('cd '..nvim_dir)
-      local cmd
-      if iswin() then
-        cmd = '!shell-test UTF-8  '
-      else
-        cmd = '!./shell-test UTF-8'
-      end
+      local cmd = iswin() and '!shell-test UTF-8  ' or '!./shell-test UTF-8'
       feed_command(cmd)
       -- Note: only the first example of split composed char works
       screen:expect([[
diff --git a/test/functional/ui/searchhl_spec.lua b/test/functional/ui/searchhl_spec.lua
index cdb6256f77..c3b9af5e72 100644
--- a/test/functional/ui/searchhl_spec.lua
+++ b/test/functional/ui/searchhl_spec.lua
@@ -5,7 +5,7 @@ local command = helpers.command
 local feed_command = helpers.feed_command
 local eq = helpers.eq
 local eval = helpers.eval
-local nvim_dir = helpers.nvim_dir
+local testprg = helpers.testprg
 
 describe('search highlighting', function()
   local screen
@@ -305,7 +305,7 @@ describe('search highlighting', function()
   end)
 
   it('is preserved during :terminal activity', function()
-    feed([[:terminal "]]..nvim_dir..[[/shell-test" REP 5000 foo<cr>]])
+    feed((':terminal "%s" REP 5000 foo<cr>'):format(testprg('shell-test')))
 
     feed(':file term<CR>')
     feed('G')  -- Follow :terminal output.
diff --git a/test/functional/ui/wildmode_spec.lua b/test/functional/ui/wildmode_spec.lua
index 65c6fabfa8..98398bc7a1 100644
--- a/test/functional/ui/wildmode_spec.lua
+++ b/test/functional/ui/wildmode_spec.lua
@@ -7,7 +7,7 @@ local meths = helpers.meths
 local eq = helpers.eq
 local eval = helpers.eval
 local retry = helpers.retry
-local nvim_dir = helpers.nvim_dir
+local testprg = helpers.testprg
 
 describe("'wildmenu'", function()
   local screen
@@ -114,7 +114,7 @@ describe("'wildmenu'", function()
   it('is preserved during :terminal activity', function()
     command('set wildmenu wildmode=full')
     command('set scrollback=4')
-    feed([[:terminal "]]..nvim_dir..[[/shell-test" REP 5000 !terminal_output!<cr>]])
+    feed((':terminal "%s" REP 5000 !terminal_output!<cr>'):format(testprg('shell-test')))
     feed('G')  -- Follow :terminal output.
     feed([[:sign <Tab>]])   -- Invoke wildmenu.
     -- NB: in earlier versions terminal output was redrawn during cmdline mode.
diff --git a/test/functional/vimscript/let_spec.lua b/test/functional/vimscript/let_spec.lua
index 6e93655e32..85c9c690f9 100644
--- a/test/functional/vimscript/let_spec.lua
+++ b/test/functional/vimscript/let_spec.lua
@@ -7,7 +7,7 @@ local eval = helpers.eval
 local meths = helpers.meths
 local exec_capture = helpers.exec_capture
 local source = helpers.source
-local nvim_dir = helpers.nvim_dir
+local testprg = helpers.testprg
 
 before_each(clear)
 
@@ -59,7 +59,7 @@ describe(':let', function()
   end)
 
   it("multibyte env var to child process #8398 #9267",  function()
-    local cmd_get_child_env = "let g:env_from_child = system(['"..nvim_dir.."/printenv-test', 'NVIM_TEST_LET'])"
+    local cmd_get_child_env = ("let g:env_from_child = system(['%s', 'NVIM_TEST_LET'])"):format(testprg('printenv-test'))
     command("let $NVIM_TEST_LET = 'AìaB'")
     command(cmd_get_child_env)
     eq(eval('$NVIM_TEST_LET'), eval('g:env_from_child'))
diff --git a/test/functional/vimscript/system_spec.lua b/test/functional/vimscript/system_spec.lua
index dd1ac694e7..49b48fecd9 100644
--- a/test/functional/vimscript/system_spec.lua
+++ b/test/functional/vimscript/system_spec.lua
@@ -1,7 +1,7 @@
 local helpers = require('test.functional.helpers')(after_each)
 
 local assert_alive = helpers.assert_alive
-local nvim_dir = helpers.nvim_dir
+local testprg = helpers.testprg
 local eq, call, clear, eval, feed_command, feed, nvim =
   helpers.eq, helpers.call, helpers.clear, helpers.eval, helpers.feed_command,
   helpers.feed, helpers.nvim
@@ -32,10 +32,6 @@ describe('system()', function()
   before_each(clear)
 
   describe('command passed as a List', function()
-    local function printargs_path()
-      return nvim_dir..'/printargs-test' .. (iswin() and '.exe' or '')
-    end
-
     it('throws error if cmd[0] is not executable', function()
       eq("Vim:E475: Invalid value for argument cmd: 'this-should-not-exist' is not executable",
         pcall_err(call, 'system', { 'this-should-not-exist' }))
@@ -68,16 +64,16 @@ describe('system()', function()
 
     it('quotes arguments correctly #5280', function()
       local out = call('system',
-        { printargs_path(), [[1]], [[2 "3]], [[4 ' 5]], [[6 ' 7']] })
+        { testprg('printargs-test'), [[1]], [[2 "3]], [[4 ' 5]], [[6 ' 7']] })
 
       eq(0, eval('v:shell_error'))
       eq([[arg1=1;arg2=2 "3;arg3=4 ' 5;arg4=6 ' 7';]], out)
 
-      out = call('system', { printargs_path(), [['1]], [[2 "3]] })
+      out = call('system', { testprg('printargs-test'), [['1]], [[2 "3]] })
       eq(0, eval('v:shell_error'))
       eq([[arg1='1;arg2=2 "3;]], out)
 
-      out = call('system', { printargs_path(), "A\nB" })
+      out = call('system', { testprg('printargs-test'), "A\nB" })
       eq(0, eval('v:shell_error'))
       eq("arg1=A\nB;", out)
     end)
@@ -169,7 +165,7 @@ describe('system()', function()
         end
       end)
 
-      it('works with powershell', function()
+      it('with powershell', function()
         helpers.set_shell_powershell()
         eq('a\nb\n', eval([[system('Write-Output a b')]]))
         eq('C:\\\n', eval([[system('cd c:\; (Get-Location).Path')]]))
@@ -177,12 +173,11 @@ describe('system()', function()
       end)
     end
 
-    it('works with powershell w/ UTF-8 text (#13713)', function()
+    it('powershell w/ UTF-8 text #13713', function()
       if not helpers.has_powershell() then
         pending("not tested; powershell was not found", function() end)
         return
       end
-      -- Should work with recommended config used in helper
       helpers.set_shell_powershell()
       eq('ああ\n', eval([[system('Write-Output "ああ"')]]))
       -- Sanity test w/ default encoding
@@ -432,7 +427,7 @@ describe('system()', function()
   end)
 
   it("with a program that doesn't close stdout will exit properly after passing input", function()
-    local out = eval(string.format("system('%s', 'clip-data')", nvim_dir..'/streams-test'))
+    local out = eval(string.format("system('%s', 'clip-data')", testprg('streams-test')))
     assert(out:sub(0, 5) == 'pid: ', out)
     os_kill(out:match("%d+"))
   end)
@@ -611,17 +606,16 @@ describe('systemlist()', function()
   end)
 
   it("with a program that doesn't close stdout will exit properly after passing input", function()
-    local out = eval(string.format("systemlist('%s', 'clip-data')", nvim_dir..'/streams-test'))
+    local out = eval(string.format("systemlist('%s', 'clip-data')", testprg('streams-test')))
     assert(out[1]:sub(0, 5) == 'pid: ', out)
     os_kill(out[1]:match("%d+"))
   end)
 
-  it('works with powershell w/ UTF-8 text (#13713)', function()
+  it('powershell w/ UTF-8 text #13713', function()
     if not helpers.has_powershell() then
       pending("not tested; powershell was not found", function() end)
       return
     end
-    -- Should work with recommended config used in helper
     helpers.set_shell_powershell()
     eq({iswin() and 'あ\r' or 'あ'}, eval([[systemlist('Write-Output あ')]]))
     -- Sanity test w/ default encoding
@@ -633,28 +627,30 @@ describe('systemlist()', function()
 
 end)
 
-it(':{range}! works with powershell for filter and redirection #16271', function()
-  clear()
-  if not helpers.has_powershell() then
-    pending("not tested; powershell was not found", function() end)
-    return
-  end
-  local screen = Screen.new(500, 8)
-  screen:attach()
-  helpers.set_shell_powershell()
-  insert([[
-    3
-    1
-    4
-    2]])
-  feed(':4verbose %!sort<cr>')
-  screen:expect{
-    any=[[Executing command: "Start%-Process sort %-RedirectStandardInput .* %-RedirectStandardOutput .* %-NoNewWindow %-Wait".*4 lines filtered.*Press ENTER or type command to continue]]
-  }
-  feed('<CR>')
-  expect([[
-    1
-    2
-    3
-    4]])
+describe('shell :!', function()
+  before_each(clear)
+
+  it(':{range}! with powershell filter/redirect #16271', function()
+    local screen = Screen.new(500, 8)
+    screen:attach()
+    local found = helpers.set_shell_powershell(true)
+    insert([[
+      3
+      1
+      4
+      2]])
+    feed(':4verbose %!sort<cr>')
+    screen:expect{
+      any=[[Executing command: .?Start%-Process sort %-RedirectStandardInput .* %-RedirectStandardOutput .* %-NoNewWindow %-Wait]]
+    }
+    feed('<CR>')
+    if found then
+      -- Not using fake powershell, so we can test the result.
+      expect([[
+        1
+        2
+        3
+        4]])
+    end
+  end)
 end)