Game loop stripping doesn't make sense with module-style require()
The docs currently suggest that a library can take the form of a cart with a game loop that runs tests on the library, and the require() statement ignores the game loop when the library is included. This doesn't make sense with a module-style Lua file, which has a return statement at the end that cannot appear that way in a cart directly.

At the very least, the docs should be cleaned up to not recommend using these features together. It's possible that this feature isn't useful at all and should be removed. It might be a better recommendation to have a test cart that require()'s the library under test in a more traditional way.