As @sodapopcan wrote, having all those references to the schema module outside of the quote block means that no compile-time dependency to it is established for the Testbed module itself. If you need to import/require functions/macros from it in Testbed, do so inside the quote block, otherwise having ensure_compiled! in there should do the trick, too.
awerment
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sodapopcan
I really wouldn’t advise using ensure_compiled unless there is a really good reason to do so. OP is looking to create a compile-time dependency between two modules which is exactly what require and import do. Both will ensure their given modules are already compiled before the module they live in is. There are possibilities here where it might be needed but I’m not seeing that based on the provided code.
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awerment
import/require would pull in functions/macros, too though, right? Curious what the best way would be to ensure a compile-time dependency without having that?
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sodapopcan
import yes, require no. require literally just ensures the module is compiled (namely that its macros have been expanded) before the module it’s called in, ie, required for the current module to work 
It’s needed if there are macros in the dependency otherwise simply calling a function from it will suffice. For example:
defmodule Foo do
Bar.a_regular_ol_function_that_is_called_in_the_module_body_for_some_reason()
end
This will make Bar a dependency of Foo. It doesn’t need a require if Bar isn’t calling a macro.
(sorry for all the edits if you noticed that, my dog is bugging me to go outside but wanted to finish the response, lol)
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