diff --git a/test/client/uv_stream.lua b/test/client/uv_stream.lua
index 29918c576a..9074fd7687 100644
--- a/test/client/uv_stream.lua
+++ b/test/client/uv_stream.lua
@@ -149,9 +149,9 @@ ProcStream.__index = ProcStream
 --- @param argv string[]
 --- @param env string[]?
 --- @param io_extra uv.uv_pipe_t?
---- @param on_exit fun(closed: integer?)?  Called after the child process exits.
---- @param forward_stderr forward stderr from the nvim process. otherwise collect it.
+--- @param on_exit fun(closed: integer?)? Called after the child process exits.
 --- `closed` is the timestamp (uv.now()) when close() was called, or nil if it wasn't.
+--- @param forward_stderr boolean? Forward child process stderr, otherwise collect it.
 --- @return test.ProcStream
 function ProcStream.spawn(argv, env, io_extra, on_exit, forward_stderr)
   local self = setmetatable({
diff --git a/test/cmakeconfig/paths.lua.in b/test/cmakeconfig/paths.lua.in
index 2984200952..bfc1f47426 100644
--- a/test/cmakeconfig/paths.lua.in
+++ b/test/cmakeconfig/paths.lua.in
@@ -1,6 +1,6 @@
 local M = {}
 
-M.include_paths = {}
+M.include_paths = {} --- @type string[]
 for p in ("${TEST_INCLUDE_DIRS}" .. ";"):gmatch("[^;]+") do
   table.insert(M.include_paths, p)
 end
diff --git a/test/functional/terminal/tui_spec.lua b/test/functional/terminal/tui_spec.lua
index 09ac12b0ab..db92f14dc0 100644
--- a/test/functional/terminal/tui_spec.lua
+++ b/test/functional/terminal/tui_spec.lua
@@ -543,7 +543,7 @@ end
 describe('TUI', function()
   local screen --[[@type test.functional.ui.screen]]
   local child_session --[[@type test.Session]]
-  local child_exec_lua
+  local child_exec_lua --[[@type fun(code: string, ...):any]]
 
   before_each(function()
     clear()
@@ -2987,8 +2987,8 @@ describe('TUI UIEnter/UILeave', function()
 end)
 
 describe('TUI FocusGained/FocusLost', function()
-  local screen
-  local child_session
+  local screen --[[@type test.functional.ui.screen]]
+  local child_session --[[@type test.Session]]
 
   before_each(function()
     clear()
@@ -3181,7 +3181,7 @@ end)
 
 -- These tests require `tt` because --headless/--embed does not initialize the TUI.
 describe("TUI 't_Co' (terminal colors)", function()
-  local screen
+  local screen --[[@type test.functional.ui.screen]]
 
   local function assert_term_colors(term, colorterm, maxcolors)
     clear({ env = { TERM = term }, args = {} })
@@ -3199,7 +3199,7 @@ describe("TUI 't_Co' (terminal colors)", function()
       },
     })
 
-    local tline
+    local tline --[[@type string]]
     if maxcolors == 8 then
       tline = '{112:~                                                 }'
     elseif maxcolors == 16 then
@@ -3460,7 +3460,7 @@ end)
 
 -- These tests require `tt` because --headless/--embed does not initialize the TUI.
 describe("TUI 'term' option", function()
-  local screen
+  local screen --[[@type test.functional.ui.screen]]
 
   local function assert_term(term_envvar, term_expected)
     clear()
@@ -3511,7 +3511,7 @@ end)
 
 -- These tests require `tt` because --headless/--embed does not initialize the TUI.
 describe('TUI', function()
-  local screen
+  local screen --[[@type test.functional.ui.screen]]
 
   -- Runs (child) `nvim` in a TTY (:terminal), to start the builtin TUI.
   local function nvim_tui(extra_args)
diff --git a/test/functional/testterm.lua b/test/functional/testterm.lua
index f0051536d0..2ee9cfa2b5 100644
--- a/test/functional/testterm.lua
+++ b/test/functional/testterm.lua
@@ -33,6 +33,8 @@ function M.feed_csi(data)
   M.feed_termcode('[' .. data)
 end
 
+--- @param session test.Session
+--- @return fun(code: string, ...):any
 function M.make_lua_executor(session)
   return function(code, ...)
     local status, rv = session:request('nvim_exec_lua', code, { ... })
diff --git a/test/functional/ui/screen.lua b/test/functional/ui/screen.lua
index 33f5273f93..89f6e80e0e 100644
--- a/test/functional/ui/screen.lua
+++ b/test/functional/ui/screen.lua
@@ -447,6 +447,7 @@ end
 --- @field mouse_enabled? boolean
 ---
 --- @field win_viewport? table<integer,table<string,integer>>
+--- @field win_viewport_margins? table<integer,table<string,integer>>
 --- @field win_pos? table<integer,table<string,integer>>
 --- @field float_pos? [integer,integer]
 --- @field hl_groups? table<string,integer>
diff --git a/test/testutil.lua b/test/testutil.lua
index fb018a3e9e..7a4a9b9aac 100644
--- a/test/testutil.lua
+++ b/test/testutil.lua
@@ -49,7 +49,7 @@ function M.fix_slashes(obj)
 end
 
 --- @param ... string|string[]
---- @return string
+--- @return string[]
 function M.argss_to_cmd(...)
   local cmd = {} --- @type string[]
   for i = 1, select('#', ...) do
diff --git a/test/unit/preprocess.lua b/test/unit/preprocess.lua
index 906e4a2f5d..4b10918c2d 100644
--- a/test/unit/preprocess.lua
+++ b/test/unit/preprocess.lua
@@ -163,8 +163,7 @@ end
 --- @param hdr string
 --- @return string[]?
 function Gcc:dependencies(hdr)
-  --- @type string
-  local cmd = argss_to_cmd(self.path, { '-M', hdr }) .. ' 2>&1'
+  local cmd = table.concat(argss_to_cmd(self.path, { '-M', hdr }), ' ') .. ' 2>&1'
   local out = assert(io.popen(cmd))
   local deps = out:read('*a')
   out:close()
diff --git a/test/unit/testutil.lua b/test/unit/testutil.lua
index a9f8705748..b23c85d3b0 100644
--- a/test/unit/testutil.lua
+++ b/test/unit/testutil.lua
@@ -201,8 +201,10 @@ local function is_child_cdefs()
   return os.getenv('NVIM_TEST_MAIN_CDEFS') ~= '1'
 end
 
--- use this helper to import C files, you can pass multiple paths at once,
--- this helper will return the C namespace of the nvim library.
+--- use this helper to import C files, you can pass multiple paths at once,
+--- this helper will return the C namespace of the nvim library.
+---
+--- @param ... string
 local function cimport(...)
   local previous_defines --- @type string
   local preprocess_cache --- @type table<string,string>