diff --git a/test/functional/lua/treesitter_spec.lua b/test/functional/lua/treesitter_spec.lua
index 700e4599f2..5a53ca1425 100644
--- a/test/functional/lua/treesitter_spec.lua
+++ b/test/functional/lua/treesitter_spec.lua
@@ -15,9 +15,7 @@ before_each(clear)
 describe('treesitter API', function()
   -- error tests not requiring a parser library
   it('handles missing language', function()
-      local path_pat = 'Error executing lua: '..(iswin() and '.+\\vim\\' or '.+/vim/')
-
-    matches(path_pat..'treesitter.lua:39: no such language: borklang',
+    eq('Error executing lua: .../treesitter.lua: no such language: borklang',
        pcall_err(exec_lua, "parser = vim.treesitter.create_parser(0, 'borklang')"))
 
     -- actual message depends on platform
diff --git a/test/functional/lua/utility_functions_spec.lua b/test/functional/lua/utility_functions_spec.lua
index dfcbcf06eb..a51334398c 100644
--- a/test/functional/lua/utility_functions_spec.lua
+++ b/test/functional/lua/utility_functions_spec.lua
@@ -10,7 +10,6 @@ local feed = helpers.feed
 local pcall_err = helpers.pcall_err
 local exec_lua = helpers.exec_lua
 local matches = helpers.matches
-local iswin = helpers.iswin
 
 before_each(clear)
 
@@ -148,9 +147,11 @@ describe('lua stdlib', function()
     ]])
     eq({"yy","xx"}, exec_lua("return test_table"))
 
-    -- type checked args
-    eq('Error executing lua: vim.schedule: expected function', pcall_err(exec_lua, "vim.schedule('stringly')"))
-    eq('Error executing lua: vim.schedule: expected function', pcall_err(exec_lua, "vim.schedule()"))
+    -- Validates args.
+    eq('Error executing lua: vim.schedule: expected function',
+      pcall_err(exec_lua, "vim.schedule('stringly')"))
+    eq('Error executing lua: vim.schedule: expected function',
+      pcall_err(exec_lua, "vim.schedule()"))
 
     exec_lua([[
       vim.schedule(function()
@@ -223,12 +224,14 @@ describe('lua stdlib', function()
       matches(".*Infinite loop detected", pcall_err(split, t[1], t[2]))
     end
 
-    -- type checked args
+    -- Validates args.
     eq(true, pcall(split, 'string', 'string', nil))
-    local path_pattern = iswin() and '[a-zA-Z]:[^:]+:%d+:' or '[^:]+:%d+:'
-    matches("Error executing lua: "..path_pattern.." Expected string, got number", pcall_err(split, 1, 'string', nil))
-    matches("Error executing lua: "..path_pattern.." Expected string, got number", pcall_err(split, 'string', 1, nil))
-    matches("Error executing lua: "..path_pattern.." Expected boolean or nil, got number", pcall_err(split, 'string', 'string', 1))
+    eq('Error executing lua: .../shared.lua: Expected string, got number',
+      pcall_err(split, 1, 'string', nil))
+    eq('Error executing lua: .../shared.lua: Expected string, got number',
+      pcall_err(split, 'string', 1, nil))
+    eq('Error executing lua: .../shared.lua: Expected boolean or nil, got number',
+      pcall_err(split, 'string', 'string', 1))
   end)
 
   it('vim.trim', function()
@@ -247,9 +250,9 @@ describe('lua stdlib', function()
       assert(t[2], trim(t[1]))
     end
 
-    -- type checked args
-    local path_pattern = iswin() and '[a-zA-Z]:[^:]+:%d+:' or '[^:]+:%d+:'
-    matches("Error executing lua: "..path_pattern.." Expected string, got number", pcall_err(trim, 2))
+    -- Validates args.
+    eq('Error executing lua: .../shared.lua: Expected string, got number',
+      pcall_err(trim, 2))
   end)
 
   it('vim.inspect', function()
@@ -289,15 +292,11 @@ describe('lua stdlib', function()
   end)
 
   it('vim.pesc', function()
-    local pesc = function(s)
-      return exec_lua('return vim.pesc(...)', s)
-    end
+    eq('foo%-bar', exec_lua([[return vim.pesc('foo-bar')]]))
+    eq('foo%%%-bar', exec_lua([[return vim.pesc(vim.pesc('foo-bar'))]]))
 
-    eq('foo%-bar', pesc('foo-bar'))
-    eq('foo%%%-bar', pesc(pesc('foo-bar')))
-
-    -- type checked args
-    local path_pattern = iswin() and '[a-zA-Z]:[^:]+:%d+:' or '[^:]+:%d+:'
-    matches("Error executing lua: "..path_pattern.." Expected string, got number", pcall_err(pesc, 2))
+    -- Validates args.
+    eq("Error executing lua: .../shared.lua: Expected string, got number",
+      pcall_err(exec_lua, [[return vim.pesc(2)]]))
   end)
 end)
diff --git a/test/helpers.lua b/test/helpers.lua
index 4c526d217f..3f29a28c0d 100644
--- a/test/helpers.lua
+++ b/test/helpers.lua
@@ -74,7 +74,8 @@ function module.matches(pat, actual)
   error(string.format('Pattern does not match.\nPattern:\n%s\nActual:\n%s', pat, actual))
 end
 
--- Invokes `fn` and returns the error string, or raises an error if `fn` succeeds.
+-- Invokes `fn` and returns the error string (may truncate full paths), or
+-- raises an error if `fn` succeeds.
 --
 -- Usage:
 --    -- Match exact string.
@@ -88,7 +89,17 @@ function module.pcall_err(fn, ...)
   if status == true then
     error('expected failure, but got success')
   end
+  -- From this:
+  --    /home/foo/neovim/runtime/lua/vim/shared.lua:186: Expected string, got number
+  -- to this:
+  --     Expected string, got number
   local errmsg = tostring(rv):gsub('^[^:]+:%d+: ', '')
+  -- From this:
+  --    Error executing lua: /very/long/foo.lua:186: Expected string, got number
+  -- to this:
+  --    Error executing lua: .../foo.lua:186: Expected string, got number
+  errmsg = errmsg:gsub([[lua: [a-zA-Z]?:?[^:]-[/\]([^:/\]+):%d+: ]], 'lua: .../%1: ')
+  --                          ^ Windows drive-letter (C:)
   return errmsg
 end