Script for checking if string methods behave the same as regular Lua

stringmethodtest.lua

--@shared
local setfenv = setfenv or debug.setfenv
assert(setfenv, "incompatible version of lua")
local prefix = BRANCH and (SERVER and "GLUA SERVER" or CLIENT and "GLUA CLIENT") or (SERVER and "SF SERVER" or CLIENT and "SF CLIENT") or "LUA"
prefix = prefix..": "
local i = 0
local j = 0
local k = 7
local function test(cond, msg)
	j = j+1
	if cond then
		i = i+1
	else
		print(prefix.."Failed test "..j..": "..msg)
	end
end
local function callback(err, stacktrace)
	-- I really, really, really don't like Starfall's custom 'error' objects.
	err = type(err) == "table" and err.message or err
	err = err:gsub("^.-: ", "")
	print(prefix.."Error: "..err)
end
local function custom(str) end

-- Adding new functions to the 'string' table makes them accessible as methods
string.custom = custom
test(string.custom == custom, "custom string function")
test(xpcall(function()
	assert(("foo").custom == custom)
end, callback), "custom string method")
string.custom = nil

-- Overriding functions in the 'string' table also overrides methods
do
	local reverse = string.reverse
	string.reverse = custom
	test(string.reverse == custom, "overridden string function")
	test(xpcall(function()
		assert(("foo").reverse == custom)
	end, callback), "overridden string method")
	string.reverse = reverse
end

-- If you replace the 'string' table outright, Lua will not switch to it
do
	local oldstring = string
	string = {
		custom = custom
	}
	test(xpcall(function()
		assert(string.custom == custom)
		assert(("foo").custom ~= custom)
	end, callback), "replaced string table")
	string = oldstring
end

-- If you sandbox it though, it will still use the parent environment's 'string' table
local function func()
	assert(string.custom == custom)
	assert(("foo").custom ~= custom)
end
setfenv(func, {
	assert = assert,
	string = {
		custom = custom
	}
})
test(xpcall(func, callback), "sandboxed string method")

-- Lua won't use a local 'string' table
do
	local string = {
		custom = custom
	}
	test(xpcall(function()
		assert(string.custom == custom)
		assert(("foo").custom ~= custom)
	end, callback), "local string table")
end

print(prefix..(i == j and "PASSED" or "FAILED")..": passed "..i.."/"..k.." tests")