diff --git a/build.zig b/build.zig
index 424c00c091..b999631951 100644
--- a/build.zig
+++ b/build.zig
@@ -408,6 +408,7 @@ pub fn test_config(b: *std.Build, gen_dir: LazyPath) ![]u8 {
         \\local M = {{}}
         \\
         \\M.include_paths = {{}}
+        \\M.apple_sysroot = ""
         \\M.translations_enabled = "$ENABLE_TRANSLATIONS" == "ON"
         \\M.is_asan = "$ENABLE_ASAN_UBSAN" == "ON"
         \\M.is_zig_build = true
diff --git a/cmake/RunTests.cmake b/cmake/RunTests.cmake
index fc4c2c587a..6d123060b6 100644
--- a/cmake/RunTests.cmake
+++ b/cmake/RunTests.cmake
@@ -78,7 +78,6 @@ execute_process(
     ${TEST_PATH}
   TIMEOUT $ENV{TEST_TIMEOUT}
   WORKING_DIRECTORY ${WORKING_DIR}
-  ERROR_VARIABLE err
   RESULT_VARIABLE res
   ${EXTRA_ARGS})
 
@@ -87,11 +86,6 @@ file(REMOVE_RECURSE ${RM_FILES})
 
 if(res)
   message(STATUS "Tests exited non-zero: ${res}")
-  if("${err}" STREQUAL "")
-    message(STATUS "No output to stderr.")
-  else()
-    message(STATUS "Output to stderr:\n${err}")
-  endif()
 
   # Dump the logfile on CI (if not displayed and moved already).
   if(CI_BUILD)
diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index f6112a3c2a..e59be46314 100644
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -481,11 +481,13 @@ foreach(target ${targets})
     message(STATUS "${target} props '${prop}'")
     foreach(gen_include ${prop})
       list(APPEND gen_cflags "-I${gen_include}")
+      list(APPEND TEST_INCLUDE_DIRS "${gen_include}")
     endforeach()
   endif()
 endforeach()
 
 list(REMOVE_DUPLICATES gen_cflags)
+list(REMOVE_DUPLICATES TEST_INCLUDE_DIRS)
 
 if(APPLE AND CMAKE_OSX_SYSROOT)
   list(APPEND gen_cflags "-isysroot" "${CMAKE_OSX_SYSROOT}")
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 8db05ac839..1141e6aded 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,6 +1,6 @@
 add_subdirectory(functional/fixtures)  # compile test programs
 
-get_target_property(TEST_INCLUDE_DIRS main_lib INTERFACE_INCLUDE_DIRECTORIES)
+get_directory_property(TEST_INCLUDE_DIRS DIRECTORY ${PROJECT_SOURCE_DIR}/src/nvim DEFINITION TEST_INCLUDE_DIRS)
 
 set(TEST_OPTIONS
       -D BUILD_DIR=${CMAKE_BINARY_DIR}
diff --git a/test/cmakeconfig/paths.lua.in b/test/cmakeconfig/paths.lua.in
index 56d3257bcf..2984200952 100644
--- a/test/cmakeconfig/paths.lua.in
+++ b/test/cmakeconfig/paths.lua.in
@@ -4,6 +4,7 @@ M.include_paths = {}
 for p in ("${TEST_INCLUDE_DIRS}" .. ";"):gmatch("[^;]+") do
   table.insert(M.include_paths, p)
 end
+M.apple_sysroot = "${CMAKE_OSX_SYSROOT}"
 
 M.translations_enabled = "${ENABLE_TRANSLATIONS}" == "ON"
 M.is_asan = "${ENABLE_ASAN_UBSAN}" == "ON"
diff --git a/test/testutil.lua b/test/testutil.lua
index 62cf1b18ca..fb018a3e9e 100644
--- a/test/testutil.lua
+++ b/test/testutil.lua
@@ -5,17 +5,6 @@ local Paths = require('test.cmakeconfig.paths')
 
 luaassert:set_parameter('TableFormatLevel', 100)
 
-local quote_me = '[^.%w%+%-%@%_%/]' -- complement (needn't quote)
-
---- @param str string
---- @return string
-local function shell_quote(str)
-  if string.find(str, quote_me) or str == '' then
-    return '"' .. str:gsub('[$%%"\\]', '\\%0') .. '"'
-  end
-  return str
-end
-
 --- Functions executing in the context of the test runner (not the current nvim test session).
 --- @class test.testutil
 local M = {
@@ -66,19 +55,15 @@ function M.argss_to_cmd(...)
   for i = 1, select('#', ...) do
     local arg = select(i, ...)
     if type(arg) == 'string' then
-      cmd[#cmd + 1] = shell_quote(arg)
+      cmd[#cmd + 1] = arg
     else
       --- @cast arg string[]
       for _, subarg in ipairs(arg) do
-        cmd[#cmd + 1] = shell_quote(subarg)
+        cmd[#cmd + 1] = subarg
       end
     end
   end
-  return table.concat(cmd, ' ')
-end
-
-function M.popen_r(...)
-  return io.popen(M.argss_to_cmd(...), 'r')
+  return cmd
 end
 
 --- Calls fn() until it succeeds, up to `max` times or until `max_ms`
@@ -356,7 +341,7 @@ function M.check_logs()
           local status, f
           local out = io.stdout
           if os.getenv('SYMBOLIZER') then
-            status, f = pcall(M.popen_r, os.getenv('SYMBOLIZER'), '-l', file)
+            status, f = pcall(M.repeated_read_cmd, os.getenv('SYMBOLIZER'), '-l', file)
           end
           out:write(start_msg .. '\n')
           if status then
@@ -539,16 +524,37 @@ end
 
 --- @return string?
 function M.repeated_read_cmd(...)
-  for _ = 1, 10 do
-    local stream = M.popen_r(...)
-    local ret = stream:read('*a')
-    stream:close()
-    if ret then
-      return ret
+  local cmd = M.argss_to_cmd(...)
+  local data = {}
+  local got_code = nil
+  local stdout = assert(vim.uv.new_pipe(false))
+  local handle = assert(
+    vim.uv.spawn(
+      cmd[1],
+      { args = vim.list_slice(cmd, 2), stdio = { nil, stdout, 2 }, hide = true },
+      function(code, _signal)
+        got_code = code
+      end
+    )
+  )
+  stdout:read_start(function(err, chunk)
+    if err or chunk == nil then
+      stdout:read_stop()
+      stdout:close()
+    else
+      table.insert(data, chunk)
     end
+  end)
+
+  while not stdout:is_closing() or got_code == nil do
+    vim.uv.run('once')
   end
-  print('ERROR: Failed to execute ' .. M.argss_to_cmd(...) .. ': nil return after 10 attempts')
-  return nil
+
+  if got_code ~= 0 then
+    error('command ' .. vim.inspect(cmd) .. 'unexpectedly exited with status ' .. got_code)
+  end
+  handle:close()
+  return table.concat(data)
 end
 
 --- @generic T
diff --git a/test/unit/api/private_helpers_spec.lua b/test/unit/api/private_helpers_spec.lua
index bdfc83a031..4d9c2e5046 100644
--- a/test/unit/api/private_helpers_spec.lua
+++ b/test/unit/api/private_helpers_spec.lua
@@ -18,7 +18,7 @@ local type_key = api_t.type_key
 local obj2lua = api_t.obj2lua
 local func_type = api_t.func_type
 
-local api = cimport('./src/nvim/api/private/t.h', './src/nvim/api/private/converter.h')
+local api = cimport('./src/nvim/api/private/helpers.h', './src/nvim/api/private/converter.h')
 
 describe('vim_to_object', function()
   local vim_to_object = function(l)
diff --git a/test/unit/api/testutil.lua b/test/unit/api/testutil.lua
index bb387ae0e1..77c9d608cf 100644
--- a/test/unit/api/testutil.lua
+++ b/test/unit/api/testutil.lua
@@ -13,8 +13,11 @@ local int_type = t_eval.int_type
 local flt_type = t_eval.flt_type
 local type_key = t_eval.type_key
 
-local api =
-  cimport('./src/nvim/api/private/defs.h', './src/nvim/api/private/t.h', './src/nvim/memory.h')
+local api = cimport(
+  './src/nvim/api/private/defs.h',
+  './src/nvim/api/private/helpers.h',
+  './src/nvim/memory.h'
+)
 
 local obj2lua
 
diff --git a/test/unit/preprocess.lua b/test/unit/preprocess.lua
index 8d481df0d0..6114f43ad7 100644
--- a/test/unit/preprocess.lua
+++ b/test/unit/preprocess.lua
@@ -146,13 +146,20 @@ end
 
 --- @param ... string
 function Gcc:add_to_include_path(...)
+  local ef = self.preprocessor_extra_flags
   for i = 1, select('#', ...) do
     local path = select(i, ...)
-    local ef = self.preprocessor_extra_flags
     ef[#ef + 1] = '-I' .. path
   end
 end
 
+function Gcc:add_apple_sysroot(sysroot)
+  local ef = self.preprocessor_extra_flags
+
+  table.insert(ef, '-isysroot')
+  table.insert(ef, sysroot)
+end
+
 -- returns a list of the headers files upon which this file relies
 --- @param hdr string
 --- @return string[]?
@@ -278,4 +285,9 @@ function M.add_to_include_path(...)
   return cc:add_to_include_path(...)
 end
 
+--- @param ... string
+function M.add_apple_sysroot(...)
+  return cc:add_apple_sysroot(...)
+end
+
 return M
diff --git a/test/unit/testutil.lua b/test/unit/testutil.lua
index a38e602ac8..3c40f7062e 100644
--- a/test/unit/testutil.lua
+++ b/test/unit/testutil.lua
@@ -19,6 +19,11 @@ for _, p in ipairs(paths.include_paths) do
   Preprocess.add_to_include_path(p)
 end
 
+-- add some nonstandard header locations
+if paths.apple_sysroot ~= '' then
+  Preprocess.add_apple_sysroot(paths.apple_sysroot)
+end
+
 local child_pid = nil --- @type integer?
 --- @generic F: function
 --- @param func F
diff --git a/test/unit/vterm_spec.lua b/test/unit/vterm_spec.lua
index c5293a21cb..aab895b7dc 100644
--- a/test/unit/vterm_spec.lua
+++ b/test/unit/vterm_spec.lua
@@ -94,7 +94,7 @@ local vterm = t.cimport(
   './src/nvim/vterm/screen.h',
   './src/nvim/vterm/state.h',
   './src/nvim/vterm/vterm.h',
-  './src/nvim/vterm/vterm_internal.h',
+  './src/nvim/vterm/vterm_internal_defs.h',
   './test/unit/fixtures/vterm_test.h'
 )