OK, right.

I still can't get the test result I expect in this case...

But as a general matter, I have noted the general disdain Rubyists have
for abstract class-like enforcement mechanisms. And it's true that if I
want to rule out runtime errors by enforcing the presence of certain
parent class methods in any implementing children, then I've got to put
all this stuff in the parent to ensure that, as I have been trying to do
with the Module hooks.

ALTERNATIVE APPROACH -- which I take to be more Ruby -- is to trust the
implementer to follow the documentation for the parent -- taking
responsibility for runtime error stuff, themselves. I might try to help
them by adding test examples that they can take from my parent module
and run against their child implementations.

Is my alternative approach the way to go, or do good Rubyists enforce
parent module contracts to avoid runtime errors in the implementing 
children?

Grar

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