Note that fetching any title besides the one for the current page is
considered "expensive". It also records the title fetched in the
ParserOutput so it will be listed in pagelinks, just like #ifexists.
This also moves the ToString test formatter into TestFramework.lua, so
TitleLibraryTests.lua can use it too.
Change-Id: I799f3289a37fe1349b6bca5758829acf82cb718f
Rework the LuaEngine tests to be entirely modular, so that every library
need not add itself to one monolithic file. This also allows other
extensions that add Lua modules to make unit tests without having to
somehow inject them into a test class owned by Scribunto.
The approach taken is similar to that used for Selenium for running
tests against multiple browsers.
Change-Id: I294b2a8195759c0e4fa211f879305a8eb66d9c9a
